THE GABCIKOVO-NAGYMAROS PROJECT

INTERNATIONAL COURT OF JUSTICE
REPORTS OF JUDGMENTS,ADVISORY OPINIONS AND ORDERS CASE CONCERNING
THE GABCIKOVO-NAGYMAROS PROJECT
(HUNGARYISLOVAKIA)
JUDCMENT OF 25 SEPTEMBER 1997

Official citation :
GabCikovo-Nagymaros Project (HungarylSlovakia),
Judgment, 1. C. J. Reports 1997, p. 7
ISSN 0074-4441
ISBN 92-1-070757-5
Sales number: 692

25 SEPTEMBER 1997
JUDGMENT

GABC~KOVO-NACYMAROS PROJECT
(HUNGARYISLOVAKIA)

1997
25 September
General List
No. 92

Treaty of 16 September 1977 concerning the construction and operation of
the GabCikovo-Nugymaros Systenz of Locks - "Related instruments".
Suspension and abandonment by Hungary, in 1989, oj'works on the Project
- Applicability of the Vienna Convention of 1969 on the Law of Treaties -
Law of treaties and law of State responsibility - Stute of necessity as a ground
jor precluding the wrongfulness of an act - "Essential interest" of the State
committing the act - Environment - "Grave und imminent peril" - Act
having to constitute the "only means" of saj&guarding the interest threatened -
State having "contributed to the occurrence of the state of necessity".
Czechoslovakia:~pr oceeding, in November 1991, to "Variant C" andputting
into operation, from October 1992, this Variant - Arguments drawn from a
proposed principle of approximate application - Respect for the limits of the
Treaty - Right to an equitahle and reasonable share of rhe resources of an
international wutercourse - Commission of a wrongful act andprior conduct of
a prepararory character - Obligation to mitigate damages - Principle concerning
only the calculation of damages - Countermeasures - Response to an
internationally wrongful act - Proportionality - Assumption of unilateral
control of a shared resource.
Notification by Hungary, on 19 May 1992, of the fermination of the 1977
Treaty and reluted instruments - Legal efjrects - Matter falling within the law
of treaties - Articles 60 to 62 of the Vienna Convention on the Law of Trearies
- Customury law - lmpossihility of performance - Permanent disappearance
or destruction of an "object" indispensable for execution - Impossibility of prrformance
resulting from the hreach, by the party invoking il, of an obligation
under the Treaty - Fundamental change of circumstances - Essential basis of
the consent of the parties - Extent of obligations still to be performed - Stability
of treaty relations - Material breach of the Treaty - Date on which the
breach occurred and date of notijïcation of termination - Victim of a breach
having itselfcommitted a prior breach of the Treaty - Emergence of new norms
of environmental law - Sustainable development - Treaty provisions permit
GABC~KOVO-NAGYMPARORJOECST (JUDGMENT)
ting the parties, by mutual consent, to take account of those norms - Repudiation
of the Treaty - Reciprocal non-compliance - Integrity of the rule pacta
sunt servanda - Treaty remaining in force until terminated by mutual consent.
Legal consequences of the Judgment of the Court - Dissolution of Czechoslovakia
- Article 12 of the Vienna Convention of 1978 on Succession of States
in respect of' Treaties - Customary laiv - Succession of States without effect
on a treaty creating rights and obligations "attaching" to the territory -
Irregular state of uffairs as a result of failure of both Parties to comply with
their treaty obligations - Ex injuria jus non oritur - Objectives of the Treaty
- Obligations overtaken by events - Positions adopted by the parties after
conclusion of the Treaty - Good faith negotiations - Effects of the Project on
the environment - Agreed solution to be found by the Parties - Joint régime
- Reparation for arts committed by both Parties - Co-operation in the use of
shared water resources - Damages - Succession in respect of rights and obligations
relating to the Project - Intersecting ivrongs - Settlement of accounts
for the construction of the works.

JUDGMENT
Present: President SCHWEBELVi;c e-President WEERAMANTRJuYd;g es ODA,
BEDIAOUIG, UILLAUMRE,A NJEVAH, ERCZEGHS,H I, FLEISCHHAUER,
KOROMAV, ERESHCHETPINA,R RA-ARANGURKEONO, IJMANRS,E ZEK;
Judge ad hoc SKUBISZEW; RSeKgIi strar VALENCIA-OSPINA

In the case concerning the GabCikovo-Nagymaros Project,
between
the Republic of Hungary,
represented by
H.E. Mr. Gyorgy Szénasi, Ambassador, Head of the International Law
Department, Ministry of Foreign Affairs,
as Agent and Counsel;
H.E. Mr. Dénes Tomaj, Ambassador of the Republic of Hungary to the
Netherlands,
as Co-Agent ;
Mr. James Crawford, Whewell Professor of International Law, University of
Cambridge,
Mr. Pierre-Marie Dupuy, Professor at the University Panthéon-Assas
(Paris II) and Director of the Institut des hautes études internationales
of Paris,
Mr. Alexandre Kiss, Director of Research, Centre national de la recherche
scientifique (retd.),
Mr. Laszlo Valki, Professor of International Law, Eotvos Lorand University,
Budapest,
Mr. Boldizsar Nagy, Associate Professor of International Law, Eotvos
Lorand University, Budapest,
Mr. Philippe Sands, Reader in International Law, University of London,
School of Oriental and African Studies, and Global Professor of Law,
New York University,
Ms Katherine Gorove, consulting Attorney,
as Counsel and Advocates;
Dr. Howard Wheater, Professor of Hydrology, Imperia1 College, London,
Dr. Gabor Vida, Professor of Biology, Eotvos Lorand University, Budapest,
Member of the Hungarian Academy of Sciences,
Dr. Roland Carbiener, Professor emeritus of the University of Strasbourg,
Dr. Klaus Kern, consulting Engineer, Karlsruhe,
as Advocates;
Mr. Edward Helgeson,
Mr. Stuart Oldham,
Mr. Péter Molnar,
as Advisers;
Dr. Gyorgy Kovacs,
Mr. Timothy Walsh,
Mr. Zoltan Kovacs,
as Technical Advisers ;
Dr. Attila Nyikos,
as Assistant ;
Mr. Axe1 Gosseries, LL.M.,
as Translator ;
Ms Éva Kocsis,
Ms Katinka Tompa,
as Secretaries,
and
the Slovak Republic,
represented by
H.E. Dr. Peter Tomka, Ambassador, Legal Adviser of the Ministry of Foreign
Affairs,
as Agent;
Dr. Vaclav Mikulka, Member of the International Law Commission,
as Co-Agent, Counsel and Advocate;
Mr. Derek W. Bowett, C.B.E., Q.C., F.B.A., Whewell Professor emeritus of
International Law at the University of Cambridge, former Member of the
International Law Commission,
as Counsel ;
Mr. Stephen C. McCaffrey, Professor of International Law at the University
of the Pacific, McGeorge School of Law, Sacramento, United States of
America, former Member of the International Law Commission,
Mr. Alain Pellet, Professor at the University of Paris X-Nanterre and at the

Institute of Political Studies, Paris, Member of the International Law
Commission,
Mr. Walter D. Sohier, Member of the Bar of the State of New York and of
the District of Columbia,
Sir Arthur Watts, K.C.M.G., Q.C., Barrister, Member of the Bar of England
and Wales,
Mr. Samuel S. Wordsworth, avocat à la cour d'appel de Paris, Solicitor of
the Supreme Court of England and Wales, Frere Cholmeley, Paris,
as Counsel and Advocates;
Mr. Igor Mucha, Professor of Hydrogeology and Former Head of the
Groundwater Department at the Faculty of Natural Sciences of Comenius
University in Bratislava,
Mr. Karra Venkateswara Rao, Director of Water Resources Engineering,
Department of Civil Engineering, City University, London,
Mr. Jens Christian Refsgaard, Head of Research and Development, Danish
Hydraulic Institute,
as Counsel and Experts;
Dr. Cecilia KandraCova, Director of Department, Ministry of Foreign
Affairs,
Mr. Ludëk Krajhanzl, Attorney at Law, Vyroubal Krajhanzl Skacel and
Partners, Prague,
Mr. Miroslav LiSka, Head of the Division for Public Relations and Expertise,
Water Resources Development State Enterprise, Bratislava,
Dr. Peter VrSansky, Minister-Counsellor, Chargé d'affaires a.i., of the
Embassy of the Slovak Republic, The Hague,
as Counsellors ;
Miss Anouche Beaudouin, allocataire de recherche at the University of
Paris X-Nanterre,
Ms Cheryl Dunn, Frere Cholmeley, Paris,
Ms Nikoleta GI!ndova, attaché, Ministry of Foreign Affairs,
Mr. Drahoslav Stefanek, attaché, Ministry of Foreign Affairs,
as Legal Assistants,
composed as above,
after deliberation,
delivers the following Judgment ;
1. By a letter dated 2 July 1993, filed in the Registry of the Court on the
same day, the Ambassador of the Republic of Hungary (hereinafter called
"Hungary") to the Netherlands and the Chargé d'affaires ad interim of the Slovak
Republic (hereinafter called "Slovakia") to the Netherlands jointly notified
to the Court a Special Agreement in English that had been signed at Brussels
on 7 April 1993 and had entered into force on 28 June 1993, on the date of the
exchange of instruments of ratification.
2. The text of the Special Agreement reads as follows:

"The Republic of Hungary and the Slovak Rcpublic,
Considering that differences have arisen between the Czech and Slovak
Federal Republic and the Republic of Hungary regarding the implementation
and the termination of the Treaty on the Construction and Operation
of the Gabtikovo-Nagymaros Barrage System signed in Budapest on
16 September 1977 and related instruments (hereinafter referred to as 'the
Treaty'), and on the construction and operation of the 'provisional solution';
Beuring in nlind that the Slovak Republic is one of the two successor
States of the Czech and Slovak Federal Republic and the sole successor
State in respect of rights and obligations relating to the GabCikovo-Nagymaros
Project ;
Recognizing that the Parties concerned have been unable to settle these
differences by negotiations;
Huving in rnind that both the Czechoslovak and Hungarian delegations
expressed their commitment to submit the differences connected with the
GabCikovo-Nagymaros Project in al1 its aspects to binding international
arbitration or to the International Court of Justice;
Desiring that these differences should be settled by the International
Court of Justice;
Reculling their commitment to apply, pending the Judgment of the
International Court of Justice, such a temporary water management régime
of the Danube as shall be agreed between the Parties;
Desiring further to define the issues to be submitted to the International
Court of Justice.
Have agreed as follows :
Article I
The Parties submit the questions contained in Article 2 to the International
Court of Justice pursuant to Article 40, paragraph 1, of the Statute
of the Court.
Article 2
(1) The Court is requested to decide on the basis of the Treaty and rules
and principles of general international law. as well as such other treaties as
the Court may find applicable,
( a ) whether the Republic of Hungary was entitled to suspend and subsequently
abandon, in 1989, the works on the Nagymaros Project and
on the part of the GabCikovo Project for which the Treaty attributed
responsibility to the Republic of Hungary:
(b) whether the Czech and Slovak Federal Republic was entitled to proceed,
in November 1991, to the 'provisional solution' and to put into
operation from October 1992 this system, described in the Report of
the Working Group of Independent Experts of the Commission of
the European Communities, the Republic of Hungary and the Czech
and Slovak Federal Republic dated 23 November 1992 (damming up
of the Danube at river kilometre 185 1.7 on Czechoslovak territory
and resulting consequences on water and navigation coufse);

(c) what are the legal effects of the notification, on 19 May 1992, of the
termination of the Treaty by the Republic of Hungary.
(2) The Court is also requested to determine the legal consequences,
including the rights and obligations for the Parties, arising from its Judgment
on the questions in paragraph 1 of this Article.
Article 3
(1) Al1 questions of procedure and evidence shall be regulated in accordance
with the provisions of the Statute and the Rules of Court.
(2) However. the Parties request the Court to order that the written
proceedings should consist of:
(LI) a Memorial presented by each of the Parties not later than ten
months after the date of notification of this Special Agreement to the
Registrar of the International Court of Justice;
( h i a Counter-Memorial presented by each of the Parties not later than
seven months after the date on which each has received the certified
copy of the Memorial of the other Party;
( c i a Reply presented by each of the Parties within such time-limits as the
Court may order.
(d) The Court may request additional written pleadings by the Parties if
it so determines.
(3) The above-mentioned parts of the written proceedings and their
annexes presented to the Registrar will not be transmitted to the other
Party until the Registrar has received the corresponding part of the proceedings
from the said Party.
Article 4
(1) The Parties agree that, pending the final Judgment of the Court,
they will establish and implement a temporary water management régime
for the Danube.
(2) They further agree that, in the period before such a régime is established
or implemented, if either Party believes its rights are endangered by
the conduct of the other, it may request immediate consultation and reference,
if necessary, to experts, including the Commission of the European
Communities, with a view to protecting those rights; and that protection
shall not be sought through a request to the Court under Article 41 of the
Statute.
(3) This commitment is accepted by both Parties as fundamental to the
conclusion and continuing validity of the Special Agreement.
Article 5
(1) The Parties shall accept the Judgment of the Court as final and binding
upon them and shall execute it in its entirety and in good faith.
(2) Immediately after the transmission of the Judgment the Parties shall
enter into negotiations on the modalities for its execution.
(3) If they are unable to reach agreement within six months, either
Party may request the Court to render an additional Judgment to determine
the modalities for executing its Judgment.
Article 6
(1) The present Special Agreement shall be subject to ratification.

(2) The instruments of ratification shall be exchanged as soon as possible
in Brussels.
(3) The present Special Agreement shall enter into force on the date of
exchange of instruments of ratification. Thereafter it will be notified jointly
to the Registrar of the Court.
In witness whereof the undersigned being duly authorized thereto, have
signed the present Special Agreement and have affixed thereto their seals."
3. Pursuant to Article 40, paragraph 3, of the Statute and Article 42 of the
Rules of Court, copies of the notification and of the Special Agreement were
transmitted by the Registrar to the Secretary-General of the United Nations,
Members of the United Nations and other States entitled to appear before the
Court.
4. Since the Court included upon the Bench no judge of Slovak nationality,
Slovakia exercised its right under Article 31, paragraph 2, of the Statute to
choose a judge ad hoc to sit in the case: it chose Mr. Krzysztof Jan Skubiszewski.
5. By an Order dated 14 July 1993, the Court fixed 2 May 1994 as the timelimit
for the filing by each of the Parties of a Memorial and 5 December 1994
for the filing by each of the Parties of a Counter-Memorial. having regard to
the provisions of Article 3, paragraph 2 (a) and (b), of the Special Agreement.
Those pleadings were duly filed within the prescribed time-limits.
6. By an Order dated 20 December 1994, the President of the Court,
having heard the Agents of the Parties, fixed 20 June 1995 as the time-limit
for the filing of the Replies, having regard to the provisions of Article 3, paragraph
2 (c), of the Special Agreement. The Replies were duly filed within the
time-limit thus prescribed and, as the Court had not asked for the submission
of additional pleadings, the case was then ready for hearing.
7. By letters dated 27 January 1997, the Agent of Slovakia, referring to the
provisions of Article 56, paragraph 1, of the Rules of Court, expressed his Government's
wish to produce two new documents; by a letter dated 10 February
1997, the Agent of Hungary declared that his Government objected to their
production. On 26 February 1997, after having duly ascertained the views of
the two Parties, the Court decided, in accordance with Article 56, paragraph 2,
of the Rules of Court, to authorize the production of those documents under
certain conditions of which the Parties were advised. Within the time-limit fixed
by the Court to that end, Hungary submitted comments on one of those documents
under paragraph 3 of that same Article. The Court authorized Slovakia
to comment in turn upon those observations, as it had expressed a wish to do
so; its comments were received within the time-limit prescribed for that purpose.
8. Moreover, each of the Parties asked to be allowed to show a video cassette
in the course of the oral proceedings. The Court agreed to those requests,
provided that the cassettes in question were exchanged in advance between the
Parties, through the intermediary of the Registry. That exchange was effected
accordingly.
9. In accordance with Article 53, paragraph 2, of the Rules of Court. the
Court decided, after having ascertained the views of the Parties. that copies of
the pleadings and documents annexed would be made available to the public as
from the opening of the oral proceedings.
10. By a letter dated 16 June 1995, the Agent of Slovakia invited the Court

to visit the locality to which the case relates and there to exercise its functions
with regard to the obtaining of evidence, in accordance with Article 66 of the
Rules of Court. For his part, the Agent of Hungary indicated, by a letter dated
28 June 1995, that, if the Court should decide that a visit of that kind would be
useful, his Government would be pleased to co-operate in organizing it. By a
letter dated 14 November 1995, the Agents of the Parties jointly notified to the
Court the text of a Protocol of Agreement, concluded in Budapest and New
York the same day, with a view to proposing to the Court the arrangements
that might be made for such a visit in situ; and, by a letter dated 3 February
1997, they jointly notified to it the text of Agreed Minutes drawn up in Budapest
and New York the same day, which supplemented the Protocol of Agreement
of 14 November 1995. By an Order dated 5 February 1997, the Court
decided to accept the invitation to exercise its functions with regard to the
obtaining of evidence at a place to which the case relates and, to that end, to
adopt the arrangements proposed by the Parties. The Court visited the area
from 1 to 4 April 1997; it visited a number of locations along the Danube and
took note of the technical explanations given by the representatives who had
been designated for the purpose by the Parties.
I l . The Court held a first round of ten public hearings from 3 to 7 March
and from 24 to 27 March 1997, and a second round of four public hearings on
10, 1 1, 14 and 15 April 1997, after having made the visit in situ referred to in
the previous paragraph. During those hearings, the Court heard the oral arguments
and replies of:
For Hungary: H.E. Mr. Szénasi,
Professor Valki,
Professor Kiss,
Professor Vida,
Professor Carbiener,
Professor Crawford,
Professor Nagy,
Dr. Kern,
Professor Wheater,
Ms Gorove.
Professor Dupuy,
Professor Sands.
For Slovakia: H.E. Dr. Tomka,
Dr. Mikulka,
Mr. Wordsworth,
Professor McCaffrey,
Professor Mucha,
Professor Pellet,
Mr. Refsgaard,
Sir Arthur Watts.
12. The Parties replied orally and in writing to various questions put by
Members of the Court. Referring to the provisions of Article 72 of the Rules of
Court, each of the Parties submitted to the Court its comments upon the replies
given by the other Party to some of those questions.

13. In the course of the written proceedings, the following submissions were
presented by the Parties:
On hekaif of Hungary,
in the Memorial, the Counter-Memorial and the Reply (mutatis mutandis identicai
texts) :
"On the basis of the evidence and legal argument presented in the
Memorial, Counter-Memorial and this Reply, the Republic of Hungary
Reyuests the Court to rrdjudge and declare
First, that the Republic of Hungary was entitled to suspend and subsequently
abandon the works on the Nagymaros Project and on the part of
the Gabtikovo Project for which the Treaty attributed responsibility to the
Republic of Hungary;
Second, that the Czech and Slovak Federal Republic was not entitled to
proceed to the 'provisional solution' (damming up of the Danube at river
kilometre 185 1.7 on Czechoslovak territory and resulting consequences on
water and navigation course);
Tizird, that by its Declaration of 19 May 1992, Hungary validly terminated
the Treaty on the Construction and Operation of the Gabtikovo-
Nagymaros Barrage System of 16 September 1977:
Rrqzre.~ts the Court to adjzldge and declare furtller
that the legal consequences of these findings and of the evidence and the
arguments presented to the Court are as follows:
(1) that the Treaty of 16 September 1977 has never been in force between
the Republic of Hungary and the Slovak Republic;
(2) that the Slovak Republic bears responsibility to the Republic of Hungary
for maintaining in operation the 'provisional solution' referred to
above ;
(3) that the Slovak Republic is internationally responsible for the damage
and loss suffered by the Republic of Hungary and by its nationals as a
result of the 'provisional solution';
(4) that the Slovak Republic is under an obligation to make reparation in
respect of such damage and loss, the amount of such reparation, if it
cannot be agreed by the Parties within six months of the date of the
Judgment of the Court, to be deterrnined by the Court;
(5) that the Slovak Republic is under the following obligations:
( a ) to return the waters of the Danube to their course along the
international frontier between the Republic of Hungary and the
Slovak Republic, that is to Say the main navigable channel as
defined by applicable treaties;
(b) to restore the Danube to the situation it was in prior to the
putting into effect of the provisional solution: and
( c ) to provide appropriate guarantees against the repetition of the
damage and loss suffered by the Republic of Hungary and by its
nationals."

On behaif of Slovakia,
in the Memorial, the Counter-Memorial and the Reply (mutatis mutandis identical
texts) :
"On the basis of the evidence and legal arguments presented in the Slovak
Memorial, Counter-Memorial and in this Reply, and reserving the
right to supplement or amend its claims in the light of further written
pleadings, the Slovak Republic
Requests fhe Court to udjudge and declare:
1. That the Treaty between Czechoslovakia and Hungary of 16 September
1977 concerning the construction and operation of the Gabtikovol
Nagymaros System of Locks, and related instruments, and to which the
Slovak Republic is the acknowledged successor, is a treaty in force and
has been so from the date of its conclusion; and that the notification of
termination by the Republic of Hungary on 19 May 1992 was without
legal effect.
2. That the Republic of Hungary was not entitled to suspend and subsequently
abandon the works on the Nagymaros Project and on that part
of the Gabtikovo Project for which the 1977 Treaty attributed responsibility
to the Republic of Hungary.
3. That the act of proceeding with and putting into operation Variant C,
the 'provisional solution', was lawful.
4. That the Republic of Hungary must therefore cease forthwith al1 conduct
which impedes the full and bona fide implementation of the 1977
Treaty and must take al1 necessary steps to fulfil its own obligations
under the Treaty without further delay in order to restore compliance
with the Treaty.
5. That, in consequence of its breaches of the 1977 Treaty, the Republic of
Hungary is liable to pay, and the Slovak Republic is entitled to receive,
full compensation for the loss and damage caused to the Slovak Republic
by those breaches, plus interest and loss of profits, in the amounts
to be determined by the Court in a subsequent phase of the proceedings
in this case."
14. In the oral proceedings. the following submissions were presented by the
Parties
On behaif of Huagury,
at the hearing of 1 1 April 1997:
The submissions read at the hearing were mutatis mutandis identical to those
presented by Hungary during the written proceedings.
On behalf of' Slovakia,
at the hearing of 15 April 1997 :
"On the basis of the evidence and legal arguments presented in its written
and oral pleadings, the Slovak Republic,
Requests the Court to adjudge and declare:
1. That the Treaty, as defined in the first paragraph of the Preamble to the
Compromis between the Parties, dated 7 April 1993, concerning the
construction and operation of the GabtikovolNagymaros System of
Locks and related instruments, concluded between Hungary and Czechoslovakia and with regard to which the Slovak Republic is the
successor State, has never ceased to be in force and so remains, and
that the notification of 19 May 1992 of purported termination of the
Treaty by the Republic of Hungary was without legal effect;
2. That the Republic of Hungary was not entitled to suspend and subsequently
abandon the works on the Nagymaros Project and on that part
of the Gabeikovo Project for which the 1977 Treaty attributes responsibility
to the Republic of Hungary;
3. That the Czech and Slovak Federal Republic was entitled, in November
1991, to proceed with the 'provisional solution' and to put this system
into operation from October 1992; and that the Slovak Republic
was, and remains, entitled to continue the operation of this system;
4. That the Republic of Hungary shall therefore cease forthwith al1 conduct
which impedes the bona fide implementation of the 1977 Treaty
and shall take al1 necessary steps to fulfil its own obligations under the
Treaty without further delay in order to restore compliance with the
Treaty, subject to any amendments which may be agreed between the
Parties ;
5. That the Republic of Hungary shall give appropriate guarantees that it
will not impede the performance of the Treaty, and the continued
operation of the system;
6. That, in consequence of its breaches of the 1977 Treaty, the Republic of
Hungary shall, in addition to immediately resuming performance of its
Treaty obligations, pay to the Slovak Republic full compensation for
the loss and damage, including loss of profits, caused by those breaches
together with interest thereon;
7. That the Parties shall immediately begin negotiations with a view, in
particular, to adopting a new timetable and appropriate measures for
the implementation of the Treaty by both Parties, and to fixing the
amount of compensation due by the Republic of Hungary to the Slovak
Republic; and that. if the Parties are unable to reach an agreement
within six months, either one of them may request the Court to render
an additional Judgment to determine the modalities for executing its
Judgment."
15. The present case arose out of the signature, on 16 September 1977,
by the Hungarian People's Republic and the Czechoslovak People's
Republic, of a treaty "concerning the construction and operation of the
GabEikovo-Nagymaros System of Locks" (hereinafter called the "1977
Treatv"). The names of the two contractine States have varied over the
yearst hereinafter they will be referred touas Hungary and Czechoslovakia.
The 1977 Treaty entered into force on 30 June 1978.
It provides for the construction and operation of a System of Locks by
the parties as a "joint investment". According to its Preamble, the barrage
system was designed to attain
"the broad utilization of the natural resources of the Bratislava-
Budapest section of the Danube river for the development of water resources, energy, transport, agriculture and other sectors of the
national economy of the Contracting Parties".
The joint investment was thus essentially aimed at the production of
hydroelectricity, the improvement of navigation on the relevant section
of the Danube and the protection of the areas along the banks
against flooding. At the same time, by the terms of the Treaty, the contracting
parties undertook to ensure that the quality of water in the Danube
was not impaired as a result of the Project, and that compliance with
the obligations for the protection of nature arising in connection with the
construction and operation of the System of Locks would be observed.
16. The Danube is the second longest river in Europe, flowing along or
across the borders of nine countries in its 2,860-kilometre course from the
Black Forest eastwards to the Black Sea. For 142 kilometres, it forms the
boundary between Slovakia and Hungary. The sector with which this
case is concerned is a stretch of approximately 200 kilometres, between
Bratislava in Slovakia and Budapest in Hungary. Below Bratislava, the
river gradient decreases markedly, creating an alluvial plain of grave1 and
sand sediment. This plain is delimited to the north-east, in Slovak territory,
by the Maly Danube and to the south-west, in Hungarian territory,
by the Mosoni Danube. The boundary between the two States is constituted,
in the major part of that region, by the main channel of the river.
The area lying between the Mali Danube and that channel, in Slovak
territory, constitutes the ~ i t nOi s trov; the area between the main channe1
and the Mosoni Danube, in Hungarian territory, constitutes the.
Szigetkoz. Cunovo and, further downstream, GabCikovo, are situated in
this sector of the river on Slovak territory, Cunovo on the right bank and
GabCikovo on the left. Further downstream, after the confluence of the
various branches, the river enters Hungarian territory and the topography
becomes hillier. Nagymaros lies in a narrow valley at a bend in the
Danube just before it turns south, enclosing the large river island of Szentendre
before reaching Budapest (see sketch-map No. 1, p. 19 below).
17. The Danube has always played a vital part in the commercial and
economic development of its riparian States, and has underlined and
reinforced their interdependence, making international CO-operation
essential. Improvements to the navigation channel have enabled the Danube,
now linked by canal to the Main and thence to the Rhine, to become
an important navigational artery connecting the North Sea to the Black
Sea. In the stretch of river to which the case relates, flood protection
measures have been constructed over the centuries, farming and forestry
practised, and, more recently, there has been an increase in population
and industrial activity in the area. The cumulative effects on the river and
on the environment of various human activities over the years have not
al1 been favourable, particularly for the water régime. Only by international CO-operation could action be taken to alleviate
these problems. Water management projects along the Danube have frequently
sought to combine navigational improvements and flood protection
with the production of electricity through hydroelectric power plants.
The potential of the Danube for the production of hydroelectric power
has been extensively exploited by some riparian States. The history of
attempts to harness the potential of the particular stretch of the river at
issue in these proceedings extends over a 25-year period culminating in
the signature of the 1977 Treaty.
18. Article 1, paragraph 1, of the 1977 Treaty describes the principal
works to be constructed in pursuance of the Project. It provided for the
building of two series of locks, one at Gabëikovo (in Czechoslovak territory)
and the other at Nagymaros (in Hungarian territory), to constitute
"a single and indivisible operational system of works" (see sketchmap
No. 2, p. 21 below). The Court will subsequently have occasion to
revert in more detail to those works, which were to comprise, inter alia, a
reservoir upstream of Dunakiliti, in Hungarian and Czechoslovak territory;
a dam at Dunakiliti, in Hungarian territory; a bypass canal, in
Czechoslovak territory, on which was to be constructed the Gabcikovo
System of Locks (together with a hydroelectric power plant with an
installed capacity of 720 megawatts (MW)); the deepening of the bed of
the Danube downstream of the place at which the bypass canal was to
rejoin the old bed of the river; a reinforcement of flood-control works
along the Danube upstream of Nagymaros; the Nagymaros System of
Locks, in Hungarian territory (with a hydroelectric power plant of a
capacity of 158 MW); and the deepening of the bed of the Danube down-
Stream.
Article 1, paragraph 4, of the Treaty further provided that the technical
specifications concerning the system would be included in the "Joint
Contractual Plan" which was to be drawn up in accordance with the
Agreement signed by the two Governments for this purpose on 6 May
1976; Article 4, paragraph 1, for its part, specified that "the joint investment
[would] be carried out in conformity with the joint contractual
plan".
According to Article 3, paragraph 1 :
"Operations connected with the realization of the joint investment
and with the performance of tasks relating to the operation of the
System of Locks shall be directed and supervised by the Governments
of the Contracting Parties through . . . (. . . 'government
delegates')."
Those delegates had, inter alia, "to ensure that construction of the System
of Locks is . . . carried out in accordance with the approved joint
contractual plan and the project work schedule". When the works were
brought into operation, they were moreover "To establish the operating and operational procedures of the System of Locks and ensure compliance
therewith."
Article 4, paragraph 4, stipulated that:
"Operations relating to the joint investment [should] be organized
by the Contracting Parties in such a way that the power generation
plants [would] be put into service during the period 1986-1990."
Article 5 provided that the cost of the joint investment would be borne
by the contracting parties in equal measure. It specified the work to be
carried out by each one of them. Article 8 further stipulated that the
Dunakiliti dam, the bypass canal and the two series of locks at Gab-
Cikovo and Nagymaros would be "jointly owned" by the contracting
parties "in equal measure". Ownership of the other works was to be
vested in the State on whose territory they were constructed.
The parties were likewise to participate in equal measure in the use of
the system put in place, and more particularly in the use of the base-load
and peak-load power generated at ,the hydroelectric power plants
(Art. 9).
According to Article 10, the works were to be managed by the State on
whose territory they were located, "in accordance with the jointly-agreed
operating and operational procedures", while Article 12 stipulated that
the operation, maintenance (repair) and reconstruction costs of jointly
- owned works of the System of Locks were also to be borne jointly by the
contracting parties in equal measure.
According to Article 14,
"The discharge specified in the water balance of the approved
joint contractual plan shall be ensured in the bed of the Danube
[between Dunakiliti and Sap] unless natural conditions or other circumstances
temporarily require a greater or smaller discharge."
Paragraph 3 of that Article was worded as follows:
"In the event that the withdrawal of water in the Hungarian-
Czechoslovak section of the Danube exceeds the quantities of water
specified in the water balance of the approved joint contractual plan
and the excess withdrawal results in a decrease in the output of
electric power, the share of electric power of the Contracting Party
benefiting from the excess withdrawal shall be correspondingly
reduced."
Article 15 specified that the contracting parties
"shall ensure, by the means specified in the joint contractual plan,
that the quality of the water in the Danube is not impaired as a
result of the construction and operation of the System of Locks". Article 16 set forth the obligations of the contracting parties concerning
the maintenance of the bed of the Danube.
Article 18, paragraph 1, provided as follows :
"The Contracting Parties, in conformity with the obligations previously
assumed by them, and in particular with article 3 of the Convention
concerning the regime of navigation on the Danube, signed
at Belgrade on 18 August 1948, shall ensure uninterrupted and safe
navigation on the international fairway both during the construction
and during the operation of the System of Locks."
It was stipulated in Article 19 that:
"The Contracting Parties shall, through the means specified in the
joint contractual plan, ensure compliance with the obligations for
the protection of nature arising in connection with the construction
and operation of the System of Locks."
Article 20 provided for the contracting parties to take appropriate
measures, within the framework of their national investments, for the
protection of fishing interests in conformity with the Convention concerning
Fishing in the Waters of the Danube, signed at Bucharest on
29 January 1958.
According to Article 22, paragraph 1, of the Treaty, the contracting
parties had, in connection with the construction and operation of the
System of Locks, agreed on minor revision to the course of the State
frontier between them as follows:
"(d) In the Dunakiliti-HruSov head-water area, the State frontier
shall run from boundary point 161.V.O.A. to boundary stone
No. 1.5. in a straight line in such a way that the territories
affected, to the extent of about 10-10 hectares shall be offset
between the two States."
It was further provided, in paragraph 2, that the revision of the State
frontier and the exchange of territories so provided for should be effected
"by the Contracting Parties on the basis of a separate treaty". No such
treaty was concluded.
Finally a dispute settlement provision was contained in Article 27,
worded as follows:
"1. The settlement of disputes in matters relating to the realization
and operation of the System of Locks shall be a function of the
government delegates.
2. If the government delegates are unable to reach agreement on
the matters in dispute, they shall refer them to the Governments of
the Contracting Parties for decision."
19. The Joint Contractual Plan, referred to in the previous paragraph,
set forth, on a large number of points, both the objectives of the system and the characteristics of the works. In its latest version it specified in
paragraph 6.2 that the GabCikovo bypass canal would have a discharge
capacity of 4,000 cubic metres per second (m3/s). The power plant would
include "Eight . . . turbines with 9.20 m diameter running wheels" and
would "mainly operate in peak-load time and continuously during high
water". This type of operation would give an energy production of
2,650 gigawattihours (GWh) per annum. The Plan further stipulated in
paragraph 4.4.2 :
"The low waters are stored every day, which ensures the peakload
time operation of the GabEikovo hydropower plant . . . a minimum
of 50 m3/s additional water is provided for the old bed [of the
Danube] besides the water supply of the branch system."
The Plan further specified that, in the event that the discharge into the
bypass canal exceeded 4,000-4,500 m3/s, the excess amounts of water
would be channelled into the old bed. Lastly, according to paragraph 7.7
of the Plan:
"The common operational regulation stipulates that concerning the
operation of the Dunakiliti barrage in the event of need during the
growing season 200 m3/s discharge must be released into the old Danube
bed, in addition to the occasional possibilities for rinsing the bed."
The Joint Contractual Plan also contained "Preliminary Operating and
Maintenance Rules", Article 23 of which specified that "The final operating
rules [should] be approved within a year of the setting into operation
of the system." (Joint Contractual Plan, Summary Documentation,
Vol. 0-1-A.)
Nagymaros, with six turbines, was, according to paragraph 6.3 of
the Plan, to be a "hydropower station . . . type of a basic power-station
capable of operating in peak-load time for five hours at the discharge
interval between 1,000-2,500 m3/s" per day. The intended annual production
was to be 1,025 GWh (Le., 38 per cent of the production of GabEikovo,
for an installed power only equal to 21 per cent of that of GabCikovo).
20. Thus, the Project was to have taken the form of an integrated joint
project with the two contracting parties on an equal footing in respect of
the financing, construction and operation of the works. Its single and
indivisible nature was to have been realized through the Joint Contractua1
Plan which complemented the Treaty. In particular, Hungary would
have had control of the sluices at Dunakiliti and the works at Nagymaros,
whereas Czechoslovakia would have had control of the works at
GabCikovo.
21. The schedule of work had for its part been fixed in an Agreement
on mutual assistance signed by the two parties on 16 September 1977, at the same time as the Treaty itself. The Agreement moreover made some
adjustments to the allocation of the works between the parties as laid
down by the Treaty.
Work on the Project started in 1978. On Hungary's initiative, the two
parties first agreed, by two Protocols signed on 10 October 1983 (one
amending Article 4, paragraph 4, of the 1977 Treaty and the other the
Agreement on mutual assistance), to slow the work down and to postpone
putting into operation the power plants, and then, by a Protocol
signed on 6 February 1989 (which amended the Agreement on mutual
assistance), to accelerate the Project.
22. As a result of intense criticism which the Project had generated in
Hungary, the Hungarian Government decided on 13 May 1989 to suspend
the works at Nagymaros pending the completion of various studies
which the competent authorities were to finish before 31 July 1989. On
21 July 1989, the Hungarian Government extended the suspension of the
works at Nagymaros until 31 October 1989, and, in addition, suspended
the works at Dunakiliti until the same date. Lastly, on 27 October 1989,
Hungary decided to abandon the works at Nagymaros and to maintain
the status quo at Dunakiliti.
23. During this period, negotiations were being held between the
parties. Czechoslovakia also started investigating alternative solutions.
One of them, subsequently known as "Variant CM, entailed a unilateral
diversion of the Danube by Czechoslovakia on its territory some 10 kilometres
upstream of Dunakiliti (see sketch-map Nol 3, p. 26 below). In its
final stage, Variant C included the construction at Cunovo of an overflow
dam and a levee linking that dam to the south bank of the bypass canal.
The corresponding reservoir was to have a smaller surface area and provide
approximately 30 per cent less storage than the reservoir initially
contemplated. Provision was made for ancillary works, namely: an intake
structure to supply the Mosoni Danube; a weir to enable, inter dia,
floodwater to be directed along the old bed of the Danube: an auxiliary
shiplock; and two hydroelectric power plants (one capable of an aniiual
production of 4 GWh on the Mosoni Danube, and the other with a production
of 174 GWh on the old bed of the Danube). The supply of water
to the side-arms of the Danube on the Czechoslovak bank was to be
secured by means of two intake structures in the bypass canal at
DobrohoSt' and GabEikovo. A solution was to be found for the Hungarian
bank. Moreover, the question of the deepening of the bed of the Danube
at the confluence of the bypass canal and the old bed of the river
remained outstanding.
On 23 July 1991, the Slovak Government decided "to begin, in September
1991, construction to put the GabEikovo Project into operation
by the provisional solution". That decision was endorsed by the Federal
Czechoslovak Government on 25 July. Work on Variant C began
in November 1991. Discussions continued between the two parties but to
no avail, and, on 19 May 1992, the Hungarian Government transmitted to the Czechoslovak Government a Note Verbale terminating the 1977
Treaty with effect from 25 May 1992. On 15 October 1992, Czechoslovakia
began work to enable the Danube to be closed and, starting on
23 October, proceeded to the damming of the river.
24. On 23 October 1992, the Court was seised of an "Application of
the Republic of Hungary v. The Czech and Slovak Federal Republic on
the Diversion of the Danube River"; however, Hungary acknowledged
that there was no basis on which the Court could have founded its jurisdiction
to entertain that application, on which Czechoslovakia took no
action. In the meanwhile, the Commission of the European Communities
had offered to mediate and, during a meeting of the two parties with the
Commission held in London on 28 October 1992, the parties entered into
a series of interim undertakings. They principally agreed that the dispute
would be submitted to the International Court of Justice, that a tripartite
fact-finding mission should report on Variant C not later than 31 October,
and that a tripartite group of independent experts would submit suggestions
as to emergency measures to be taken.
25. On 1 January 1993 Slovakia became an independent State. On
7 April 1993, the "Special Agreement for Submission to the International
Court of Justice of the Differences between the Republic of Hungary and
the Slovak Republic concerning the GabEikovo-Nagymaros Project" was
signed in Brussels, the text of which is reproduced in paragraph 2 above.
After the Special Agreement was notified to the Court, Hungary informed
the Court, by a letter dated 9 August 1993, that it considered its "initial
Application [to bel now without object, and . . . lapsed".
According to Article 4 of the Special Agreement, "The Parties [agreed]
that, pending the final Judgment of the Court, they [would] establish and
implement a temporary water management régime for the Danube."
However, this régime could not easily be settled. The filling of the
~ u n o v oda m had rapidly led to a major reduction in the flow and in the
level of the downstream waters in the old bed of the Danube as well as in
the side-arms of the river. On 26 August 1993, Hungary and Slovakia
reached agreement on the setting up of a tripartite group of experts (one
expert designated by each party and three independent experts designated
by the Commission of the European Communities)
"In order to provide reliable and undisputed data on the most
important effects of the current water discharge and the remedial
measures already undertaken as well as to make recommendations
for appropriate measures."
On 1 December 1993, the experts designated by the Commission of the
European Communities recommended the adoption of various measures
to remedy the situation on a temporary basis. The Parties were unable to
agree on these recommendations. After lengthy negotiations, they finally
concluded an Agreement "concerning Certain Temporary Technical Measures
and Discharges in the Danube and Mosoni branch of the Danube",

on 19 April 1995. That Agreement raised the discharge of water into the
Mosoni Danube to 43 m3/s. It provided for an annual average of 400 m3/s
in the old bed (not including flood waters). Lastly, it provided for the construction
by Hungary of a partially underwater weir near to Dunakiliti
with a view to improving the water supply to the side-arms of the Danube
on the Hungarian side. It was specified that this temporary agreement
would come to an end 14 days after the Judgment of the Court.
26. The first subparagraph of the Preamble to the Special Agreement
covers the disputes arising between Czechoslovakia and Hungary concerning
the application and termination, not only of the 1977 Treaty, but
also of "related instruments"; the subparagraph specifies that, for the
purposes of the Special Agreement, the 1977 Treaty and the said instruments
shall be referred to as "the Treaty". "The Treaty" is expressly
referred to in the wording of the questions submitted to the Court in
Article 2, paragraph 1, subparagraphs (a) and ( c i , of the Special
Agreement.
The Special Agreement however does not define the concept of "related
instruments", nor does it list them. As for the Parties, they gave some
consideration to that question - essentially in the written proceedings -
without reaching agreement as to the exact meaning of the expression or
as to the actual instruments referred to. The Court notes however that
the Parties seemed to agree to consider that that expression covers at
least the instruments linked to the 1977 Treaty which implement it, such
as the Agreement on mutual assistance of 16 September 1977 and its
amending Protocols dated, respectively, 10 October 1983 and 6 February
1989 (see paragraph 21 above), and the Agreement as to the common
operational regulations of Plenipotentiaries fulfilling duties related to the
construction and operation of the Gabtikovo-Nagymaros Barrage System
signed in Bratislava on 11 October 1979. The Court notes that Hungary,
unlike Slovakia, declined to apply the description of related instruments
to the 1977 Treaty to the Joint Contractual Plan (see paragraph 19
above), which it refused to see as "an agreement at the same level as the
other . . . related Treaties and inter-State agreements".
Lastly the Court notes that the Parties, in setting out the replies which
should in their view be given to the questions put in the Special Agree- ,
ment, concentrated their reasoning on the 1977 Treaty; and that they
would appear to have extended their arguments to "related instruments"
in considering them as accessories to a whole treaty system, whose fate
was in principle linked to that of the main part, the 1977 Treaty. The
Court takes note of the positions of the Parties and considers that it does
not need to go into this matter further at this juncture.

27. The Court will now turn to a consideration of the questions
submitted by the Parties. In terms of Article 2, paragraph 1 ( a ) , of the
Special Agreement, the Court is requested to decide first
"whether the Republic of Hungary was entitled to suspend and subsequently
abandon, in 1989, the works on the Nagymaros Project
and on the part of the GabCikovo Project for which the Treaty
attributed responsibility to the Republic of Hungary".
28. The Court would recall that the Gabrikovo-Nagymaros System of
Locks is characterized in Article 1, paragraph 1, of the 1977 Treaty as a
"single and indivisible operational system of works".
The principal works which were to constitute this system have been
described in general terms above (see paragraph 18). Details of them are
given in paragraphs 2 and 3 of Article 1 of the Treaty.
For GabMkovo, paragraph 2 lists the following works:
" ( a ) the Dunakiliti-HruSov head-water installations in the Danube
sector at r.km. (river kilometre(s)) 1860-1 842, designed for a
maximum flood stage of 13 1.10 m.B. (metres above sea-level.
Baltic system), in Hungarian and Czechoslovak territory;
(6) the Dunakiliti dam and auxiliary navigation lock at r.km.
1842, in Hungarian territory ;
( c ) the by-pass canal (head-water canal and tail-water canal) at
r.km. 1842-1 8 1 1, in Czechoslovak territory ;
(rl) series of locks on the by-pass canal, in Czechoslovak territory,
consisting of a hydroelectric power plant with installed capacity
of 720 MW, double navigation locks and appurtenances
thereto ;
(el improved old bed of the Danube at r.km. 1842-1811, in the
joint Hungarian-Czechoslovak section;
( f ) deepened and regulated bed of the Danube at r.km. 1811-
1791, in the joint Hungarian-Czechoslovak section."
For Nagymaros, paragraph 3 specifies the following works:
" ( a ) head-water installations and flood-control works in the
Danube sector at r.km. 1791-1696.25 and in the sectors of
tributaries affected by flood waters, designed for a maximum
flood stage of 107.83 m.B., in Hungarian and Czechoslovak
territory;
( 6 ) series of locks at r.km. 1696.25, in Hungarian territory, consisting
of a dam, a hydroelectric power plant with installed
capacity of 158 MW, double navigation locks and appurtenances
thereto;
( c i deepened and regulated bed of the Danube, in both its
branches, at r.km. 1696.25-1657, in the Hungarian section."

29. Moreover, the precise breakdown of the works incumbent on each
party was set out in Article 5, paragraph 5, of the 1977 Treaty, as follows:
"5. The labour and supplies required for the realization of the
joint investment shall be apportioned between the Contracting
Parties in the following manner:
(a) The Czechoslovak Party shall be responsible for:
(1) the Dunakiliti-HruSov head-water installations on the left
bank, in Czechoslovak territory ;
(2) the head-water canal of the by-pass canal, in Czechoslovak
territory ;
(3) the GabCikovo series of locks, in Czechoslovak territory ;
(4) the flood-control works of the Nagymaros head-water
installations, in Czechoslovak territory, with the exception
of the lower Ipel district;
(5) restoration of vegetation in Czechoslovak territory;
(b) The Hungarian Party shall be responsible for
(1) the Dunakiliti-HruSov head-water installations on the
right bank, in Czechoslovak territory, including the connecting
weir and the diversionary weir;
(2) the Dunakiliti-HruSov head-water installations on the
right bank, in Hungarian territory ;
(3) the Dunakiliti dam, in Hungarian territory;
(4) the tail-water canal of the by-pass canal, in Czechoslovak
territory;
(5) deepening of the bed of the Danube below Palkovicovo,
in Hungarian and Czechoslovak territory ;
(6) improvement of the old bed of the Danube, in Hungarian
and Czechoslovak territory ;
(7) operational equipment of the GabCikovo system of locks
(transport equipment, maintenance machinery), in Czechoslovak
territory ;
(8) the flood-control works of the Nagymaros head-water
installations in the lower Ipel district, in Czechoslovak
territory ;
(9) the flood-control works of the Nagymaros head-water
installations, in Hungarian territory;
(10) the Nagymaros series of locks, in Hungarian territory;
(11) deepening of the tail-water bed below the Nagymaros
system of locks, in Hungarian territory;
(12) operational equipment of the Nagymaros system of locks
(transport equipment, maintenance machinery), in Hungarian
territory ;
(13) restoration of vegetation in Hungarian territory."

30. As the Court has already indicated (see paragraph 18 above), Article
1, paragraph 4, of the 1977 Treaty stipulated in general terms that
the "technical specifications" concerning the System of Locks would be
included in the "ioint contractual dan". The schedule of work had for its
part been fixed in an Agreement on mutual assistance signed by the two
parties on 16 September 1977 (see paragraph 21 above). In accordance
with the provisions of Article 1, paragraph 1, of that Agreement, the
whole of the works of the barrage svstem were to have been comoleted in . + ,
1991. As indicated in paragraph 2 of that same article, a summary construction
schedule was appended to the Agreement, and provision was
made for a more detailed schedule to be worked out in the Joint Contractual
Plan. The Agreement of 16 September 1977 was twice amended
further. By a Protocol signed on 10 October 1983, the parties agreed first
to postpone the works and the putting into operation of the power plants
for four more years; then, by a Protocol signed on 6 February 1989, the
parties decided, conversely, to bring them forward by 15 months, the
whole system having to be operational in 1994. A new summary construction
schedule was appended to each of those Protocols; those schedules
were in turn to be implemented by means of new detailed schedules,
included in the Joint Contractual Plan.
31. In spring 1989, the work on the GabCikovo sector was well
advanced: the Dunakiliti dam was 90 per cent complete, the Gabëikovo
dam was 85 per cent complete, and the bypass canal was between 60 per
cent complete (downstream of Gabcikovo) and 95 per cent complete
(upstream of GabCikovo) and the dykes of the Dunakiliti-HruSov reservoir
were between 70 and 98 per cent complete, depending on the location.
This was not the case in the Nagymaros sector where, although
dykes had been built, the only structure relating to the dam itself was the
coffer-dam which was to facilitate its construction.
32. In the wake of the profound political and economic changes which
occurred at this time in central Europe, the Gabcikovo-Nagymaros
Project was the object, in Czechoslovakia and more particularly in Hungary,
of increasing apprehension, both within a section of public opinion
and in some scientific circles. The uncertainties not only about the economic
viability of the Project, but also, and more so, as to the guarantees
it offered for preservation of the environment, engendered a climate of
growing concern and opposition with regard to the Project.
33. It was against this background that, on 13 May 1989, the Government
of Hungary adopted a resolution to suspend works at Nagymaros,
and ordered
"the Ministers concerned to commission further studies in order to
place the Council of Ministers in a position where it can make wellfounded
suggestions to the Parliament in connection with the amendment
of the international treaty on the investment. In the interests of

the above, we must examine the international and legal consequences,
the technical considerations, the obligations related to continuous
navigation on the Danube and the environmental/ecological
and seismic impacts of the eventual stopping of the Nagymaros
investment. To be further examined are the opportunities for the
replacement of the lost electric energy and the procedures for minimising
claims for compensation."
The suspension of the works at Nagymaros was intended to last for the
duration of these studies, which were to be completed by 31 July 1989.
Czechoslovakia immediately protested and a document defining the position
of Czechoslovakia was transmitted to the Ambassador of Hungary
in Prague on 15 May 1989. The Prime Ministers of the two countries met
on 24 May 1989, but their talks did not lead to any tangible result. On
2 June, the Hungarian Parliament authorized the Government to begin
negotiations with Czechoslovakia for the purpose of modifying the 1977
Treaty.
34. At a meeting held by the Plenipotentiaries on 8 and 9 June 1989,
Hungary gave Czechoslovakia a number of assurances concerning the
continuation of works in the GabCikovo sector, and the signed Protocol
which records that meeting contains the following passage:
"The Hungarian Government Commissioner and the Hungarian
Plenipotentiary stated, that the Hungarian side will complete construction
of the GabCikovo Project in the agreed time and in accordance
with the project plans. Directives have already been given to
continue works suspended in the area due to misunderstanding."
These assurances were reiterated in a letter that the Commissioner of the
Government of Hungary addressed to the Czechoslovak Plenipotentiary
on 9 June 1989.
3.5. With regard to the suspension of work at Nagymaros, the Hungarian
Deputy Prime Minister, in a letter dated 24 June 1989 addressed to his
Czechoslovak counterpart, expressed himself in the following terms:
"The Hungarian Academy of Sciences (HAS) has studied the environmental,
ecological and water quality as well as the seismological
impacts of abandoning or implementing the Nagymaros Barrage of
the GabCikovo-Nagymaros Barrage System (GNBS).
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Having studied the expected impacts of the construction in accordance
with the original plan, the Committee [ad hoc] of the Academy
[set up for this purpose] came to the conclusion that we do not have
adequate knowledge of the consequences of environmental risks.
In its opinion, the risk of constructing the Barrage System in
accordance with the original plan cannot be considered acceptable.
Of course, it cannot be stated either that the adverse impacts will ensue for certain, therefore, according to their recommendation,
further thorough and time consuming studies are necessary."
36. The Hungarian and Czechoslovak Prime Ministers met again on
20 July 1989 to no avail. lmmediately after that meeting, the Hungarian
Government adopted a second resolution, under which the suspension of
work at Nagymaros was extended to 31 October 1989. However, this
resolution went further, as it also prescribed the suspension, until the
same date, of the "Preparatory works on the closure of the riverbed at
. . . Dunakiliti"; the purpose of this measure was to invite "international
scientific institutions [and] foreign scientific institutes and experts" to cooperate
with "the Hungarian and Czechoslovak institutes and experts"
with a view to an assessment of the ecological impact of the Project and
the "development of a technical and operational water quality guarantee
system and . . . its implementation".
37. In the ensuing period, negotiations were conducted at various levels
between the two States, but proved fruitless. Finally, by a letter dated
4 October 1989, the Hungarian Prime Minister formally proposed to
Czechoslovakia that the Nagymaros sector of the Project be abandoned
and that an agreement be concluded with a view to reducing the ecological
risks associated with the Gabëikovo sector of the Project. He proposed
that that agreement should be concluded before 30 July 1990.
The two Heads of Government met on 26 October 1989, and were
unable to reach agreement. By a Note Verbale dated 30 October 1989,
Czechoslovakia, confirming the views it had expressed during those talks,
proposed to Hungary that they should negotiate an agreement on a system
of technical, operational and ecological guarantees relating to the
Gabëikovo-Nagymaros Project, "on the assumption that the Hungarian
party will immediately commence preparatory work on the refilling of the
Danube's bed in the region of Dunakiliti". It added that the technical
principles of the agreement could be initialled within two weeks and that
the agreement itself ought to be signed before the end of March 1990.
After the principles had been initialled, Hungary "[was to] start the actual
closure of the Danube bed". Czechoslovakia further stated its willingness
to "conclu[de] . . . a separate agreement in which both parties would
oblige themselves to limitations or exclusion of peak hour operation
mode of the . . . System". It also proposed "to return to deadlines indicated
in the Protocol of October 1983", the Nagymaros construction
deadlines being thus extended by 15 months, so as to enable Hungary to
take advantage of the time thus gained to study the ecological issues and
formulate its own proposais in due time. Czechoslovakia concluded by
announcing that, should Hungary continue unilaterally to breach the
Treaty, Czechoslovakia would proceed with a provisional solution.
In the meantime, the Hungarian Government had on 27 October
adopted a further resolution, deciding to abandon the construction of the

Nagymaros dam and to leave in place the measures previously adopted
for suspending the works at Dunakiliti. Then, by Notes Verbales dated
3 and 30 November 1989, Hungary proposed to Czechoslovakia a draft
treaty incorporating its earlier proposals, relinquishing peak power operation
of the Gabëikovo power plant and abandoning the construction of
the Nagymaros dam. The draft provided for the conclusion of an agreement
on the completion of Gabëikovo in exchange for guarantees on
protection of the environment. It finally envisaged the possibility of one
or other party seising an arbitral tribunal or the International Court of
Justice in the event that differences of view arose and persisted between
the two Governments about the construction and operation of the Gab-
Cikovo dam, as well as measures to be taken to protect the environment.
Hungary stated that it was ready to proceed immediately "with the preparatory
operations for the Dunakiliti bed-decanting", but specified that
the river would not be dammed at Dunakiliti until the agreement on
guarantees had been concluded.
38. During winter 1989-1990, the political situation in Czechoslovakia
and Hungary alike was transformed, and the new Governments were
confronted with many new problems.
In spring 1990. the new Hungarian Government, in presenting its
National Renewal Programme, announced that the whole of the Gabëikovo-
Nagymaros Project was a "mistake" and that it would initiate
negotiations as soon as possible with the Czechoslovak Government "on
remedying and sharing the damages". On 20 December 1990, the Hungarian
Government adopted a resolution for the opening of negotiations
with Czechoslovakia on the termination of the Treatv, bv, mutual consent
and the conclusion of an agreement addressing the consequences of the
termination. On 15 February 1991, the Hungarian Plenipotentiary transmitted
a draft agreement along those lines to his Czechoslovak counterpart.
On the same day, the Czechoslovak President declared that the Gab-
Cikovo-Nagymaros Project constituted a "totalitarian, gigomaniac monument
which is against nature", while emphasizing that "the problem [was]
that [the Gabëikovo power plant] [had] already been built". For his part,
the Czechoslovak Minister of the Environment stated, in a speech given
to Hungarian parliamentary committees on 1 1 September 1991, that "the
G/N Project [was] an old, obsolete one", but that, if there were "many
reasons to change, modify the treaty . . . it [was] not acceptable to cancel
the treaty . . . and negotiate later on".
During the ensuing period, Hungary refrained from completing the
work for which it was still responsible at Dunakiliti. Yet it continued to
maintain the structures it had already built and, at the end of 1991, completed
the works relating to the tailrace canal of the bypass canal assigned
to it under Article 5, paragraph 5 (b), of the 1977 Treaty.

39. The two Parties to this case concur in recognizing that the 1977
Treaty, the above-mentioned Agreement on mutual assistance of 1977
and the Protocol of 1989 were validly concluded and were duly in force
when the facts recounted above took place.
Further, they do not dispute the fact that, however flexible they may
have been, these texts did not envisage the possibility of the signatories
unilaterally suspending or abandoning the work provided for therein, or
even carrying it out according to a new schedule not approved by the two
partners.
40. Throughout the proceedings, Hungary contended that, although it
did suspend or abandon certain works, on the contrary, it never suspended
the application of the 1977 Treaty itself. To justify its conduct, it
relied essentially on a "state of ecological necessity".
Hungary contended that the various installations in the GabEikovo-
Nagymaros System of Locks had been designed to enable the Gabtikovo
power plant to operate in peak mode. Water would only have come
through the plant twice each day, at times of peak power demand. Operation
in peak mode required the vast expanse (60 km') of the planned
reservoir at Dunakiliti, as well as the Nagymaros dam, which was to
alleviate the tidal effects and reduce the variation in the water level down-
Stream of Gabtikovo. Such a system, considered to be more economically
profitable than using run-of-the-river plants, carried ecological risks
which it found unacceptable.
According to Hungary, the principal ecological dangers which would
have been caused by this system were as follows. At GabMkovoi
Dunakiliti, under the original Project, as specified in the Joint Contractua1
Plan, the residual discharge into the old bed of the Danube was
limited to 50 m3/s, in addition to the water provided to the system of sidearms.
That volume could be increased to 200 m3/s during the growing
season. Additional discharges, and in particular a number of artificial
floods, could also be effected, at an unspecified rate. In these circumstances,
the groundwater level would have fallen in most of the Szigetkoz.
Furthermore, the groundwater would then no longer have been supplied
by the Danube - which, on the contrary, would have acted as a drain -
but by the reservoir of stagnant water at Dunakiliti and the side-arms
which would have become silted up. In the long term, the quality of water
would have been seriously impaired. As for the surface water, risks of
eutrophication would have arisen, particularly in the reservoir; instead of
the old Danube there would have been a river choked with sand, where
only a relative trickle of water would have flowed. The network of arms
would have been for the most part cut off from the principal bed. The
fluvial fauna and flora, like those in the alluvial plains, would have been
condemned to extinction.
As for Nagymaros, Hungary argued that, if that dam had been built,

the bed of the Danube upstream would have silted up and, consequently,
the quality of the water collected in the bank-filtered wells would have
deteriorated in this sector. What is more, the operation of the Gabëikovo
power plant in peak mode would have occasioned significant daily variations
in the water level in the reservoir upstream, which would have constituted
a threat to aquatic habitats in particular. Furthermore, the construction
and operation of the Nagymaros dam would have caused the
erosion of the riverbed downstream, along Szentendre Island. The water
level of the river would therefore have fallen in this section and the yield
of the bank-filtered wells providing two-thirds of the water supply of the
city of Budapest would have appreciably diminished. The filter layer
would also have shrunk or perhaps even disappeared, and fine sediments
would have been deposited in certain pockets in the river. For this twofold
reason, the quality of the infiltrating water would have been severely
jeopardized.
From al1 these predictions, in support of which it quoted a variety of
scientific studies, Hungary concluded that a "state of ecological necessitv"
did indeed exist in 1989.
41. In its written pleadings, Hungary also accused Czechoslovakia of
having violated various provisions of the 1977 Treaty from before 1989
- in particular Articles 15 and 19 relating, respectively, to water quality
and nature protection - in refusing to take account of the now evident
ecological dangers and insisting that the works be continued, notably at
Nagymaros. In this context Hungary contended that, in accordance with
the terms of Article 3, paragraph 2, of the Agreement of 6 May 1976 concerning
the Joint Contractual Plan, Czechoslovakia bore responsibility
for research into the Project's impact on the environment; Hungary
stressed that the research carried out by Czechoslovakia had not been
conducted adequately, the potential effects of the Project on the environment
of the construction having been assessed by Czechoslovakia only
from September 1990. However, in the final stage of its argument, Hungary
does not appear to have sought to formulate this complaint as an
independent ground formally justifying the suspension and abandonment
of the works for which it was responsible under the 1977 Treaty. Rather,
it presented the violations of the Treaty prior to 1989, which it imputes to
Czechoslovakia, as one of the elements contributing to the emergence of
a state of necessity.
42. Hungary moreover contended from the outset that its conduct in
the present case should not be evaluated only in relation to the law of
treaties. It also observed that, in accordance with the provisions of
Article 4, the Vienna Convention of 23 May 1969 on the Law of Treaties
could not be applied to the 1977 Treaty, which was concluded before that
Convention entered into force as between the parties. Hungary has
indeed acknowledged, with reference to the jurisprudence of the Court,
that in many respects the Convention reflects the existing customary law.
Hungary nonetheless stressed the need to adopt a cautious attitude, while

suggesting that the Court should consider, in each case, the conformity of
the prescriptions of the Convention with customary international law.
43. Slovakia, for its part, denied that the basis for suspending or abandoning
the performance of a treaty obligation can be found outside the
law of treaties. It acknowledged that the 1969 Vienna Convention could
not be applied as such to the 1977 Treaty, but at the same time stressed
that a number of its provisions are a reflection of pre-existing rules of
customary international law and specified that this is, in particular, the
case with the provisions of Part V relating to invalidity, termination and
suspension of the operation of treaties. Slovakia has moreover observed
that, after the Vienna Convention had entered into force for both parties,
Hungary affirmed its accession to the substantive obligations laid down
by the 1977 Treaty when it signed the Protocol of 6 February 1989 that
cut short the schedule of work: and this led it to conclude that the Vienna
Convention was applicable to'the "contractual legal régime" constituted
by the network of interrelated agreements of which the Protocol of 1989
was a part.
44. In the course of the proceedings, Slovakia argued at length that the
state of necessity upon which Hungary relied did not constitute a reason
for the suspension of a treaty obligation recognized by the law of treaties.
At the same time, it cast doubt upon whether "ecological necessity" or
"ecological risk" could, in relation to the law of State responsibility, constitute
a circumstance precluding the wrongfulness of an act.
In any event, Slovakia denied that there had been any kind of "ecological
state of necessity" in this case either in 1989 or subsequently. It
invoked the authority of various scientific studies when it claimed that
Hungary had given an exaggeratedly pessimistic description of the situation.
Slovakia did not, of course, deny that ecological problems could
have arisen. However, it asserted that they could to a large extent have
been remedied. It accordingly stressed that no agreement had been
reached with respect to the modalities of operation of the GabCikovo
power plant in peak mode, and claimed that the apprehensions of Hungary
related only to operating conditions of an extreme kind. In the same
way, it contended that the original Project had undergone various modifications
since 1977 and that it would have been possible to modify it
even further, for example with respect to the discharge of water reserved
for the old bed of the Danube, or the supply of water to the side-arms by
means of underwater weirs.
45. Slovakia moreover denied that it in any way breached the 1977
Treaty - particularly its Articles 15 and 19 - and maintained, inter dia,
that according to the terms of Article 3, paragraph 2, of the Agreement
of 6 May 1976 relating to the Joint Contractual Plan, research into the
impact of the Project on the environment was not the exclusive responsibility
of Czechoslovakia but of either one of the parties, depending on
the location of the works.
Lastly, in its turn, it reproached Hungary with having adopted its unilateral
measures of suspension and abandonment of the works in violation of the provisions of Article 27 of the 1977 Treaty (see paragraph 18
above), which it submits required prior recourse to the machinery for dispute
settlement provided for in that Article.
46. The Court has no need to dwell upon the question of the applicability
in the present case of the Vienna Convention of 1969 on the Law of
Treaties. It needs only to be mindful of the fact that it has several times
had occasion to hold that some of the rules laid down in that Convention
might be considered as a codification of existing customary law. The
Court takes the view that in many respects this applies to the provisions
of the Vienna Convention concerning the termination and the suspension
of the operation of treaties, set forth in Articles 60 to 62 (see Legal Conseyuences
for States ofthe Continued Presence of South Afiicu in Namibia
(South West Ajrica) not1vithstunding Security Council Resolution 276
(1970), Advisory Opinion, I.C.J. Reports. 1971, p. 47, and Fisheries
Jurisdiction (United Kingdom v. Iceland), Jurisdiction of the Court,
Judgment, I.C.J. Reports 1973, p. 18; see also Interpretation qf the
Agreement of 25 Murch 1951 hetitjeen the WHO and Egypt, Advisory
Opinion, 1. C. J. Reports 1980, pp. 95-96).
Neither has the Court lost sight of the fact that the Vienna Convention
is in any event applicable to the Protocol of 6 February 1989 whereby
Hungary and Czechoslovakia agreed to accelerate completion of the
works relating to the GabEikovo-Nagymaros Project.
47. Nor does the Court need to dwell upon the question of the relationship
between the law of treaties and the law of State responsibility, to
which the Parties devoted lengthy arguments, as those two branches of
international law obviously have a scope that is distinct. A determination
of whether a convention is or is not in force, and whether it has or has
not been properly suspended or denounced, is to be made pursuant to the
law of treaties. On the other hand, an evaluation of the extent to which
the suspension or denunciation of a convention, seen as incompatible
with the law of treaties, involves the responsibility of the State which proceeded
to it, is to be made under the law of state responsibility.
Thus the Vienna Convention of 1969 on the Law of Treaties confines
itself to defining - in a limitative manner - the conditions in which a
treaty may lawfully be denounced or suspended; while the effects of a
denunciation or suspension seen as not meeting those conditions are, on
the contrary, expressly excluded from the scope of the Convention by
operation of Article 73. It is moreover well established that, when a State
has committed an internationally wrongful act, its international responsibility
is likely to be involved whatever the nature of the obligation it
has failed to respect (cf. Interpretation of Peuce Treaties ivith Bulgaria,
Hungarp and Romania, Second Phase, Advisory Opinion, 1. C. J. Reports
1950, p. 228; and see Article 17 of the Draft Articles on State Responsibility provisionally adopted by the International Law Commission on
first reading, Yearbook of the International Law Commission, 1980,
Vol. I I , Part 2, p. 32).
48. The Court cannot accept Hungary's argument to the effect that, in
1989, in suspending and subsequently abandoning the works for which it
was still responsible at Nagymaros and at Dunakiliti, it did not, for al1
that, suspend the application of the 1977 Treaty itself or then reject that
Treaty. The conduct of Hungary at that time can only be interpreted as
an expression of its unwillingness to comply with at least some of the provisions
of the Treaty and the Protocol of 6 February 1989, as specified in
the Joint Contractual Plan. The effect of Hungary's conduct was to
render impossible the accomplishment of the system of works that the
Treaty expressly described as "single and indivisible".
The Court moreover observes that, when it invoked the state of necessity
in an effort to justify that conduct, Hungary chose to place itself
from the outset within the ambit of the law of State responsibility,
thereby implying that, in the absence of such a circumstance, its conduct
would have been unlawful. The state of necessity claimed by Hungary -
supposing it to have been established - thus could not permit of the conclusion
that, in 1989, it had acted in accordance with its obligations
under the 1977 Treaty or that those obligations had ceased to be binding
upon it. It would only permit the affirmation that, under the circumstances,
Hungary would not incur international responsibility by acting
as it did. Lastly, the Court points out that Hungary expressly acknowledged
that, in any event, such a state of necessity would not exempt it
from its duty to compensate its partner.
49. The Court will now consider the question of whether there was, in
1989, a state of necessity which would have permitted Hungary, without
incurring international responsibility, to suspend and abandon works
that it was committed to perform in accordance with the 1977 Treaty and
related instruments.
50. In the present case, the Parties are in agreement in considering that
the existence of a state of necessity must be evaluated in the light of the
criteria laid down by the International Law Commission in Article 33 of
the Draft Articles on the International Responsibility of States that it
adopted on first reading. That provision is worded as follows:
"Article 33. Stufe of' Necrssify
1. A state of necessity may not be invoked by a State as a ground
for precluding the wrongfulness of an act of that State not in conformity
with an international obligation of the State unless:
(a) the act was the only means of safeguarding an essential interest
of the State against a grave and imminent peril; and

(6) the act did not seriously impair an essential interest of the State
towards which the obligation existed.
2. In any case, a state of necessity may not be invoked by a State
as a ground for precluding wrongfulness:
(a) if the international obligation with which the act of the State is
not in conformity arises out of a peremptory norm of general
international law; or
(b) if the international obligation with which the act of the State is
not in conformity is laid down by a treaty which, explicitly or
implicitly, excludes the possibility of invoking the state of necessity
with respect to that obligation; or
(c) if the State in question has contributed to the occurrence of the
state of necessity." (Yearbook of the International Laiv Commission,
1980, Vol. II, Part 2, p. 34.)
In its Commentary, the Commission defined the "state of necessity" as
being
"the situation of a State whose sole means of safeguarding an essential
interest threatened by a grave and imminent peril is to adopt
conduct not in conformity with what is required of it by an international
obligation to another State" (ibid., para. 1).
It concluded that "the notion of state of necessity is . . . deeply rooted in
general legal thinking" (ibid, p. 49, para. 31).
51. The Court considers, first of all, that the state of necessity is a
ground recognized by customary international law for precluding the
wrongfulness of an act not in conformity with an international obligation.
It observes moreover that such ground for precluding wrongfulness
can only be accepted on an exceptional basis. The International Law
Commission was of the same opinion when it explained that it had opted
for a negative form of words in Article 33 of its Draft
"in order to show, by this formal means also, that the case of invocation
of a state of necessity as a justification must be considered as
really constituting an exception - and one even more rarely admissible
than is the case with the other circumstances precluding wrongfulness
. . ." (ibid, p. 51, para. 40).
Thus, according to the Commission, the state of necessity can only be
invoked under certain strictly defined conditions which must be cumulatively
satisfied; and the State concerned is not the sole judge of whether
those conditions have been met.
52. In the present case, the following basic conditions set forth in
Draft Article 33 are relevant: it must have been occasioned by an "essential
interest" of the State which is the author of the act conficting with
one of its international obligations; that interest must have been threatened
by a "grave and imminent peril"; the act being challenged must

have been the "only means" of safeguarding that interest; that act must
not have "seriously impair[ed] an essential interest" of the State towards
which the obligation existed; and the State which is the author of that act
must not have "contributed to the occurrence of the state of necessity".
Those conditions reflect customary international law.
The Court will now endeavour to ascertain whether those conditions
had been met at the time of the suspension and abandonment, by Hungary,
of the works that it was to carry out in accordance with the 1977
Treaty.
53. The Court has no difficulty in acknowledging that the concerns
expressed by Hungary for its natural environment in the region affected
by the Gabtikovo-Nagymaros Project related to an "essential interest" of
that State, within the meaning given to that expression in Article 33 of
the Draft of the International Law Commission.
The Commission, in its Commentary, indicated that one should not, in
that context, reduce an "essential interest" to a matter only of the "existence"
of the State, and that the whole question was, ultimately, to be
judged in the light of the particular case (see Yeurbook of the Internutionul
Luiv Commission, 1980, Vol. I I , Part 2, p. 49, para. 32); at the
same time, it included among the situations that could occasion a state of
necessity, "a grave danger to . . . the ecological preservation of al1 or
some of [the] territory [of a State]" (ibid, p. 35, para. 3); and specified,
with reference to State practice, that "It is primarily in the last two
decades that safeguarding the ecological balance has come to be considered
an 'essential interest' of al1 States." (Ibid., p. 39, para. 14.)
The Court recalls that it has recently had occasion to stress, in the following
terms, the great significance that it attaches to respect for the environment,
not only for States but also for the whole of mankind:
"the environment is not an abstraction but represents the living
space, the quality of life and the very health of human beings,
including generations unborn. The existence of the general obligation
of States to ensure that activities within their jurisdiction and
control respect the environment of other States or of areas beyond
national control is now part of the corpus of international law relating
to the environment." (Legality of the Threut or Use of Nuclear
Weapons, Advisoty Opinion, I. C. J. Reports 1996, pp. 241 -242,
para. 29.)
54. The verification of the existence, in 1989, of the "peril" invoked by
Hungary, of its "grave and imminent" nature, as well as of the absence of
any "means" to respond to it, other than the measures taken by Hungary
to suspend and abandon the works, are al1 complex processes.

As the Court has already indicated (see paragraphs 33 et seq.),
Hungary on several occasions expressed, in 1989, its "uncertainties" as to
the ecological impact of putting in place the GabCikovo-Nagymaros barrage
system, which is why it asked insistently for new scientific studies to
be carried out.
The Court considers, however, that, serious though these uncertainties
might have been they could not, alone, establish the objective existence of
a "peril" in the sense of a component element of a state of necessity. The
word "Deril" certainlv evokes the idea of "risk": that is vreciselv what
distinguishes "peril" from material damage. But a state of necessity could
not exist without a "Deril" dulv established at the relevant oint in time:
the mere apprehensi'on of a Possible "peril" could not Affice in that
remect. It could moreover hardlv be otherwise. when the "~eril" constituting
the state of necessity has at the same time to be "grave" and
"imminent". "Imminence" is synonymous with "immediacy" or "proximity"
and goes far beyond the concept of "possibility". As the International
Law Commission em~hasizedi n its commentarv,., the "extremelv
grave and imminent" peril must "have been a threat to the interest at
the actual time" (Yearbook of the International Laiv Commission, 1980,
Vol. I I , Part 2, p. 49, para. 33). That does not exclude, in the view of the
Court, that a "peril" appearing in the long term might be held to be
"imminent" as soon as it is established, at the relevant point in time, that
the realization of that peril, however far off it might be, is not thereby
any less certain and inevitable.
The Hungarian argument on the state of necessity could not convince
the Court unless it was at least proven that a real, "grave" and "imminent"
"peril" existed in 1989 and that the measures taken by Hungary
were the only possible response to it.
Both Parties have placed on record an impressive amount of scientific
material aimed at reinforcing their respective arguments. The Court has
given most careful attention to this material, in which the Parties have
developed their opposing views as to the ecological consequences of the
Project. It concludes, however, that, as will be shown below, it is not
necessary in order to respond to the questions put to it in the Special
Agreement for it to determine which of those points of view is scientifically
better founded.
55. The Court will begin by considering the situation at Nagymaros.
As has already been mentioned (see paragraph 40), Hungary maintained
that, if the works at Nagymaros had been carried out as planned, the
environment - and in particular the drinking water resources - in the
area would have been exposed to serious dangers on account of problems
linked to the upstream reservoir on the one hand and, on the other, the
risks of erosion of the riverbed downstream.
The Court notes that the dangers ascribed to the upstream reservoir
were mostly of a long-term nature and, above all, that they remained uncertain.
Even though the Joint Contractual Plan envisaged that the GabEikovo power plant would "mainly operate in peak-load time and continuously
during high water", the final rules of operation had not yet
been determined (see paragraph 19 above); however, any dangers associated
with the putting into service of the Nagymaros portion of the
Project would have been closely linked to the extent to which it was operated
in peak mode and to the modalities of such operation. It follows
that, even if it could have been established - which, in the Court's
appreciation of the evidence before it, was not the case - that the reservoir
would ultimately have constituted a "grave peril" for the environment
in the area, one would be bound to conclude that the peril was not
"imminent" at the time at which Hungary suspended and then abandoned
the works relating to the dam.
With regard to the lowering of the riverbed downstream of the Nagymaros
dam, the danger could have appeared at once more serious and
more pressing, in so far as it was the supply of drinking water to the city
of Budapest which would have been affected. The Court would however
point out that the bed of the Danube in the vicinity of Szentendre had
already been deepened prior to 1980 in order to extract building materials,
and that the river had from that time attained, in that sector, the
depth required by the 1977 Treaty. The peril invoked by Hungary had
thus already materialized to a large extent for a number of years, so that
it could not, in 1989, represent a peril arising entirely out of the project.
The Court would stress, however, that, even supposing, as Hungary
maintained, that the construction and operation of the dam would have
created serious risks, Hungary had means available to it, other than the
suspension and abandonment of the works, of responding to that situation.
It could for example have proceeded regularly to discharge grave1
into the river downstream of the dam. It could likewise, if necessary, have
supplied Budapest with drinking water by processing the river water in
an appropriate manner. The two Parties expressly recognized that that
possibility remained open even though - and this is not determinative of
the state of necessity - the purification of the river water, like the other
measures envisaged, clearly would have been a more costly technique.
56. The Court now comes to the GabEikovo sector. It will recall that
Hungary's concerns in this sector related on the one hand to the quality
of the surface water in the Dunakiliti reservoir, with its effects on the
quality of the groundwater in the region, and on the other hand, more
generally, to the level, movement and quality of both the surface water
and the groundwater in the whole of the Szigetkoz, with their effects on
the Sauna and flora in the alluvial plain of the Danube (see paragraph 40
above).
Whether in relation to the Dunakiliti site or to the whole of the
Szigetkoz, the Court finds here again, that the peril claimed by Hungary
was to be considered in the long term, and, more importantly, remained
uncertain. As Hungary itself acknowledges, the damage that it apprehended had primarily to be the result of some relatively slow natural
processes, the effects of which could not easily be assessed.
Even if the works were more advanced in this sector than at Nagymaros,
they had not been completed in July 1989 and, as the Court
explained in paragraph 34 above, Hungary expressly undertook to carry
on with them, early in June 1989. The report dated 23 June 1989 by the
ud hoc Committee of the Hungarian Academy of Sciences, which was
also referred to in paragraph 35 of the present Judgment, does not
express any awareness of an authenticated peril - even in the form of a
definite peril, whose realization would have been inevitable in the long
term - when it States that:
"The measuring results of an at least five-year monitoring period
following the completion of the Gabtikovo construction are indispensable
to the trustworthy prognosis of the ecological impacts of
the barrage system. There is undoubtedly a need for the establishment
and regular operation of a comprehensive monitoring system,
which must be more developed than at present. The examination of
biological indicator objects that can sensitively indicate the changes
happening in the environment, neglected till today, have to be
included."
The report concludes as follows:
"It can be stated, that the environmental, ecological and water
quality impacts were not taken into account properly during the
design and construction period until today. Because of the complexity
of the ecological processes and lack of the measured data and the
relevant calculations the environmental impacts cannot be evaluated.
The data of the monitoring system newly operating on a very limited
area are not enough to forecast the impacts probably occurring
over a longer term. In order to widen and to make the data more
frequent a further multi-year examination is necessary to decrease
the further degradation of the water quality playing a dominant role
in this question. The expected water quality influences equally the
aquatic ecosystems, the soils and the recreational and tourist
land-use."
The Court also notes that, in these proceedings, Hungary acknowledged
that, as a general rule, the quality of the Danube waters had improved
over the past 20 years, even if those waters remained subject to hypertrophic
conditions.
However "grave" it might have been, it would accordingly have been
difficult, in the light of what is said above, to see the alleged peril as sufficiently
certain and therefore "imminent" in 1989.
The Court moreover considers that Hungary could, in this context

also, have resorted to other means in order to respond to the dangers that
it apprehended. In particular, within the framework of the original
Project, Hungary seemed to be in a position to control at least partially
the distribution of the water between the bypass canal, the old bed of the
Danube and the side-arms. It should not be overlooked that the Dunakiliti
dam was located in Hungarian territory and that Hungary could construct
the works needed to regulate flows along the old bed of the Danube
and the side-arms. Moreover, it should be borne in mind that
Article 14 of the 1977 Treaty provided for the possibility that each of the
parties might withdraw quantities of water exceeding those specified in
the Joint Contractual Plan, while making it clear that, in such an event,
"the share of electric power of the Contracting Party benefiting from the
excess withdrawal shall be correspondingly reduced".
57. The Court concludes from the foregoing that, with respect to both
Nagymaros and GabCikovo, the perils invoked by Hungary, without prejudging
their possible gravity, were not sufficiently established in 1989,
nor were they "imminent"; and that Hungary had available to it at that
time means of responding to these perceived perils other than the suspension
and abandonment of works with which it had been entrusted. What
is more, negotiations were under way which might have led to a review of
the Project and the extension of some of its time-limits, without there
being need to abandon it. The Court infers from this that the respect by
Hungary, in 1989, of its obligations under the terms of the 1977 Treaty
would not have resulted in a situation "characterized so aptly by the
maxim summum jus summa injuria" ( Yearbook of the International Law
Commission, 1980, Vol. II, Part 2, p. 49, para. 31).
Moreover, the Court notes that Hungary decided to conclude the 1977
Treaty, a Treaty which - whatever the political circumstances prevailing
at the time of its conclusion - was treated by Hungary as valid and in
force until the date declared for its termination in May 1992. As can be
seen from the material before the Court, a great many studies of a scientific
and technical nature had been conducted at an earlier time, both by
Hungary and by Czechoslovakia. Hungary was, then, presumably aware
of the situation as then known, when it assumed its obligations under the
Treaty. Hungary contended before the Court that those studies had been
inadequate and that the state of knowledge at that time was not such as
to make possible a complete evaluation of the ecological implications of
the GabCikovo-Nagymaros Project. It is nonetheless the case that
although the principal object of the 1977 Treaty was the construction of
a System of Locks for the production of electricity, improvement of navigation
on the Danube and protection against flooding, the need to ensure
the protection of the environment had not escaped the parties, as can be
seen from Articles 15, 19 and 20 of the Treaty.
What is more, the Court cannot fail to note the positions taken by
Hungary after the entry into force of the 1977 Treaty. In 1983, Hungary
asked that the works under the Treaty should go forward more slowly,

for reasons that were essentially economic but also, subsidiarily, related
to ecological concerns. In 1989, when, according to Hungary itself, the
state of scientific knowledge had undergone a significant development, it
asked for the works to be speeded up, and then decided, three months
later, to suspend them and subsequently to abandon them. The Court is
not however unaware that profound changes were taking place in Hungary
in 1989, and that, during that transitory phase, it might have been
more than usually difficult to co-ordinate the different points of view prevailing
from time to time.
The Court infers from al1 these elements that, in the present case, even
if it had been established that there was. in 1989, a state of necessity
linked to the performance of the 1977 Treaty, Hungary would not have
been permitted to rely upon that state of necessity in order to justify its
failure to comply with its treaty obligations, as it had helped, by act or
omission to bring it about.
58. It follows that the Court has no need to consider whether Hungary,
by proceeding as it did in 1989, "seriously impair[ed] an essential
interest" of Czechoslovakia, within the meaning of the aforementioned
Article 33 of the Draft of the International Law Commission - a finding
which does not in any way prejudge the damage Czechoslovakia claims
to have suffered on account of the position taken by Hungary.
Nor does the Court need to examine the argument put forward by
Hungary, according to which certain breaches of Articles 15 and 19 of
the 1977 Treaty, committed by Czechoslovakia even before 1989, contributed
to the purported state of necessity; and neither does it have to
reach a decision on the argument advanced by Slovakia, according to
which Hungary breached the provisions of Article 27 of the Treaty,
in 1989, by taking unilateral measures without having previously
had recourse to the machinery of dispute settlement for which that
Article provides.
59. In the light of the conclusions reached above, the Court, in reply to
the question put to it in Article 2, paragraph 1 ( a ) , of the Special Agreement
(see paragraph 27 above), finds that Hungary was not entitled to
suspend and subsequently abandon, in 1989, the works on the Nagymaros
Project and on the part of the GabEikovo Project for which the
1977 Treaty and related instruments attributed responsibility to it.
60. By the terms of Article 2, paragraph 1 ( h ) , of the Special Agreement,
the Court is asked in the second place to decide
"(6) whether the Czech and Slovak Federal Republic was entitled
to proceed, in November 1991, to the 'provisional solution'

and to put into operation from October 1992 this system,
described in the Report of the Working Group of Independent
Experts of the Commission of the European Communities, the
Republic of Hungary and the Czech and Slovak Federal Republic
dated 23 November 1992 (damming up of the Danube at
river kilometre 185 1.7 on Czechoslovak territory and resulting
consequences on water and navigation course)".
61. The Court will recall that, as soon as Hungary suspended the
works at Nagymaros on 13 May 1989 and extended that suspension to
certain works to be carried out at Dunakiliti, Czechoslovakia informed
Hungary that it would feel compelled to take unilateral measures if Hungary
were to persist in its refusa1 to resume the works. This was inter alia
expressed as follows in Czechoslovakia's Note Verbale of 30 October
1989 to which reference is made in paragraph 37 above:
"Should the Republic of Hungary fail to meet its liabilities and
continue unilaterally to breach the Treaty and related legal documents
then the Czechoslovak party will be forced to commence a
provisional, substitute project on the territory of the Czechoslovak
Socialist Republic in order to prevent further losses. Such a provisional
project would entail directing as much water into the Gabtikovo
dam as agreed in the Joint Construction Plan."
As the Court has already indicated (see paragraph 23), various
alternative solutions were contemplated by Czechoslovakia. In September
1990, the Hungarian authorities were advised of seven hypothetical
alternatives defined by the firm of Hydroconsult of Bratislava. All of
those solutions implied an agreement between the parties, with the exception
of one variant, subsequently known as "Variant C", which was presented
as a provisional solution which could be brought about without
Hungarian CO-operation. Other contacts between the parties took place,
without leading to a settlement of the dispute. In March 1991, Hungary
acquired information according to which perceptible progress had been
made in finalizing the planning of Variant C; it immediately gave expression
to the concern this caused.
62. Inter-governmental negotiation meetings were held on 22 April
and 15 July 1991.
On 22 April 1991, Hungary proposed the suspension, until September
1993, of al1 the works begun on the basis of the 1977 Treaty, on the
understanding that the parties undertook to abstain from any unilateral
action, and that joint studies would be carried out in the interval.
Czechoslovakia maintained its previous position according to which the
studies contemplated should take place within the framework of the 1977
Treaty and without any suspension of the works.
On 15 July 1991, Czechoslovakia confirmed its intention of putting the

GabEikovo power plant into service and indicated that the available data
enabled the effects of four possible scenarios to be assessed, each of them
requiring the co-operation of the two Governments. At the same time, it
proposed the setting up of a tripartite committee of experts (Hungary,
Czechoslovakia, European Communities) which would help in the search
for technical solutions to the problems arising from the entry into operation
of the GabCikovo sector. Hungary, for its part, took the view that :
"In the case of a total lack of understanding the so-called C variation
or 'theoretical opportunity' suggested by the Czecho-Slovak
party as a unilateral solution would be such a grave transgression of
Hungarian territorial integrity and International Law for which
there is no precedent even in the practices of the formerly socialist
countries for the past 30 years";
it further proposed the setting up of a bilateral committee for the assessment
of environmental consequences, subject to work on Czechoslovak
territory being suspended.
63. By a letter dated 24 July 1991, the Government of Hungary communicated
the following message to the Prime Minister of Slovakia:
"Hungarian public opinion and the Hungarian Government
anxiously and attentively follows the [Czechoslovakian] press reports
of the unilateral steps of the Government of the Slovak Republic
in connection with the barrage system.
The preparatory works for diverting the water of the Danube near
the Dunakiliti dam through unilaterally are also alarming. These
steps are contrary to the 1977 Treaty and to the good relationship
between our nations."
On 30 July 1991 the Slovak Prime Minister informed the Hungarian
Prime Minister of
"the decision of the Slovak Government and of the Czech and Slovak
Federal Government to continue work on the GabEikovo power
plant, as a provisional solution, which is aimed at the commencement
of operations on the territory of the Czech and Slovak Federal
Republic".
On the same day, the Government of Hungary protested, by a Note Verbale,
against the filling of the headrace canal by the Czechoslovak construction
Company, by pumping water from the Danube.
By a letter dated 9 August 1991 and addressed to the Prime Minister of
Slovakia, the Hungarian authorities strenuously protested against "any
unilateral step that would be in contradiction with the interests of our
[two] nations and international law" and indicated that they considered it
"very important [to] receive information as early as possible on the

details of the provisional solution". For its part, Czechoslovakia, in a
Note Verbale dated 27 August 1991, rejected the argument of Hungary
that the continuation of the works under those circumstances constituted
a violation of international law, and made the following proposal:
"Provided the Hungarian side submits a concrete technical solution
aimed at putting into operation the Gabtikovo system of locks
and a solution of the system of locks based on the 1977 Treaty in
force and the treaty documents related to it, the Czechoslovak side is
prepared to implement the mutually agreed solution."
64. The construction permit for Variant C was issued Gn 30 October
199 1. In November 1991 construction of a dam started at Cunovo, where
both banks of the Danube are on Czechoslovak (now Slovak) territory.
In the course of a new inter-governmental negotiation meeting, on
2 December 1991, the parties agreed to entrust the task of studying the
whole of the question of the Gabtikovo-Nagymaros Project to a Joint
Expert Committee which Hungary agreed should be complemented with
an expert from the European Communities. However whereas, for Hungary,
the work of that Committee would have been meaningless if Czechoslovakia
continued construction of Variant C, for Czechoslovakia, the
suspension of the construction, even on a temporary basis, was unacceptable.
That meeting was followed by a large number of exchanges of letters
between the parties and various meetings between their representatives at
the end of 1991 and earlv in 1992. On 23 Januarv 1992. Czechoslovakia
expressed its readiness "to stop work on the provisional solution and
continue the construction upon mutual agreement" if the tripartite committee
of experts whose constitution it proposed, and the results of the
test operation of the GabCikovo part, were to "confirm that negative ecological
effects exceed its benefits". However, the positions of the parties
were by then comprehensively defined, and would scarcely develop any
further. Hungary considered, as it indicated in a Note Verbale of 14 February
1992, that Variant C was in contravention
"of [the Treaty of 19771 . . . and the convention ratified in 1976
regarding the water management of boundary waters.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
with the principles of sovereignty, territorial integrity, with the
inviolability of State borders, as well as with the general customary
norms on international rivers and the spirit of the 1948 Belgrade
Danube Convention" ;
and the suspension of the implementation of Variant C was, in its view, a
prerequisite. As for Czechoslovakia, it took the view that recourse to
Variant C had been rendered inevitable, both for economic and ecological as well as navigational reasons, because of the unlawful suspension
and abandonment by Hungary of the works for which provision was
made in the 1977 Treaty. Any negotiation had, in its view, to be conducted
within the framework of the Treaty and without the implementation
of Variant C - described as "provisional" - being called into
question.
65. On 5 August 1992, the Czechoslovak representative to the Danube
Commission informed it that "work on the severance cutting through of
the Danube's flow will begin on 15 October 1992 at the 1,851.759-kilometre
line" and indicated the measures that would be taken at the time of
the "severance". The Hungarian representative on the Commission protested
on 17 August 1992, and called for additional explanations.
During the autumn of 1992, the implementation of VariantvC was
stepped up. The operations involved in damming the Danube at Cunovo
had been scheduled by Czechoslovakia to take place during the second
half of October 1992, at a time when the waters of the river are generally
at their lowest level. On the initiative of the Commission of the European
Communities, trilateral negotiations took place in Brussels on 21 and
22 October 1992, with a view to setting up a committee of experts and
defining its terms of reference. On that date, the first phase of the operations
leading to the damming of the Danube (the reinforcement of the
riverbed and the narrowing of the principal channel) had been completed.
The closure of the bed was begun on 23 October 1992 and the
construction of the actual dam continued from 24 to 27 October 1992:
a pontoon bridge was built over the Danube on Czechoslovak territory
using river barges, large Stones were thrown into the riverbed and
reinforced with concrete, while 80 to 90 per cent of the waters of the
Danube were directed into the canal designed to supply the Gabtikovo
power plant. The implementation of Variant C did not, however, come
to an end with the diversion of the waters, as there still remained outstanding
both reinforcement work on the dam and the building of certain
auxiliary structures.
The Court has already referred in paragraph 24 to the meeting
held in London on 28 October 1992 under the auspices of the European
Communities, in the course of which the parties to the negotiations
agreed, inter dia, to entrust a tripartite Working Group composed of
independent experts (Le., four experts designated by the European Commission,
one designated by Hungary and another by Czechoslovakia)
with the task of reviewing the situation created by the implementation of
Variant C and making proposals as to urgent measures to adopt. After
having worked for one week in Bratislava and one week in Budapest, the
Working Group filed its report on 23 November 1992.
66. A summary description of the constituent elements of Variant C
appears at paragraph 23 of the present Judgment. For the purposes of
the question put to the Court, the officia1 description that should be
adopted is, according to Article 2, paragraph 1 (b), of the Special Agreement,
the one given in the aforementioned report of the Working Group of independent experts, and it should be emphasized that, according to
the Special Agreement, "Variant C" must be taken to include the consequences
"on water and navigation course" of the dam closing off the bed
of the Danube.
In the section headed "Variant C Structures and Status of Ongoing
Work", one finds, in the report of the W.orking Group, the following
passage :
"In both countries the original structures for the GabEikovo
scheme are completed except for the closure of the Danube river at
Dunakiliti and the
(1) Completion of the hydropower station (installation and testing
of turbines) at GabEikovo.
Variant C consists of a complex of structures, located in Czecho-
Slovakia . . . The construction of these are planned for two phases.
The structures include . . . :
(2) By-pass weir controlling the flow into the river Danube.
(3) Dam closing the Danubian river bed.
(4) Floodplain weir (weir in the inundation).
(5) lntake structure for the Mosoni Danube.
(6) lntake structure in the power canal.
(7) Earth barragesidykes connecting structures.
(8) Ship lock for smaller ships (1 5 m x 80 m).
(9) Spillway weir.
(10) Hydropower station.
The construction of the structures 1-7 are included in Phase 1,
while the remaining 8-10 are a part of Phase 2 scheduled for construction
1993-1995."
67. Czechoslovakia had maintained that proceeding to Variant C and
putting it into operation did not constitute internationally wrongful acts;
Slovakia adopted this argument. During the proceedings before the Court
Slovakia contended that Hungary's decision to suspend and subsequently
abandon the construction of works at Dunakiliti had made it impossible
for Czechoslovakia to carry out the works as initially contemplated by
the 1977 Treaty and that the latter was therefore entitled to proceed with
a solution which was as close to the original Project as possible. Slovakia
invoked what it described as a "principle of approximate application" to
justify the construction and operation of Variant C. It explained that this
was the only possibility remaining to it "of fulfilling not only the purposes
of the 1977 Treaty, but the continuing obligation to implement it in
good faith".
68. Slovakia also maintained that Czechoslovakia was under a duty to
mitigate the damage resulting from Hungary's unlawful actions. It claimed

that a State which is confronted with a wrongful act of another State is
under an obligation to minimize its losses and, thereby, the damages
claimable against the wrongdoing State. It argued furthermore that "Mitigation
of damages is also an aspect of the performance of obligations in
good faith." For Slovakia, these damages would have been immense in
the present case, given the investments made and the additional economic
and environmental prejudice which would have resulted from the failure
to complete the works at DunakilitiiGabEikovo and to put the system
into operation. For this reason, Czechoslovakia was not only entitled,
but even obliged, to implement Variant C.
69. Although Slovakia maintained that Czechoslovakia's conduct was
lawful, it argued in the alternative that, even were the Court to find
otherwise, the putting into operation of Variant C could still be justified
as a countermeasure.
70. Hungary for its part contended that Variant C was a material
breach of the 1977 Treaty. It considered that Variant C also violated
Czechoslovakia's obligations under other treaties, in particular the Convention
of 31 May 1976 on the Regulation of Water Management Issues
of Boundary Waters concluded at Budapest, and its obligations under
general international law.
71. Hungary contended that Slovakia's arguments rested on an erroneous
presentation of the facts and the law. Hungary denied, inter alia,
having committed the slightest violation of its treaty obligations which
could have justified the putting into operation of Variant C. It considered
that "no such rule" of "approximate application" of a treaty exists in
international law; as to the argument derived from "mitigation of damage[
s]", it claimed that this has to do with the quantification of loss, and
could not serve to excuse conduct which is substantively unlawful. Hungary
furthermore stated that Variant C did not satisfy the conditions
required by international law for countermeasures, in particular the condition
of proportionality.
72. Before dealing with the arguments advanced by the Parties, the
Court wishes to make clear that it is aware of the serious problems with
which Czechoslovakia was confronted as a result of Hungary's decision
to relinquish most of the construction of the System of Locks for which
it was responsible by virtue of the 1977 Treaty. Vast investments had
been made, the construction at GabEikovo was al1 but finished, the
bypass canal was completed, and Hungary itself, in 1991, had duly fulfilled
its obligations under the Treaty in this respect in completing work
on the tailrace canal. It emerges from the report, dated 31 October 1992,
of the tripartite fact-finding mission the Court has referred to in paragraph
24 of the present Judgment, that not using the system would haveled to considerable financial losses, and that it could have given rise to
serious problems for the environment.
73. Czechoslovakia repeatedly denounced Hungary's suspension and
abandonment of works as a fundamental breach of the 1977 Treaty and
consequently could have invoked this breach as a ground for terminating
the Treaty; but this would not have brought the Project any nearer to
completion. It therefore chose to insist on the implementation of the
Treaty by Hungary, and on many occasions called upon the latter to
resume performance of its obligations under the Treaty.
When Hungary steadfastly refused to do so - although it had expressed
its willingness to pay compensation for damage incurred by Czechoslovakia
- and when negotiations stalled owing to the diametrically opposed
positions of the parties, Czechoslovakia decided to put the GabEikovo
system into operation unilaterally, exclusively under its own control and
for its own benefit.
74. That decision went through various stages and, in the Special
Agreement, the Parties asked the Court to decide whether Czechoslovakia
"was entitled to proceed, in November 1991" to Variant C,
and "to put [it] into operation from October 1992".
75. With a view to justifying those actions, Slovakia invoked what it
described as "the principle of approximate application", expressed by
Judge Sir Hersch Lauterpacht in the following terms:
"lt is a sound principle of law that whenever a legal instrument of
continuing validity cannot be applied literally owing to the conduct of
one of the parties, it must, without allowing that party to take advantage
of its own conduct, be applied in a way approximating most
closely to its primary object. To do that is to interpret and to give
effect to the instrument - not to change it." (Adrrzissibility uf Heurings
of Petitioners by the Committee on Soutlz West Africu, I.C.J.
Reports 1956, separate opinion of Sir Hersch Lauterpacht, p. 46.)
It claimed that this is a principle of international law and a general principle
of law.
76. It is not necessary for the Court to determine whether there is a
principle of international law or a general principle of law of "approximate
application" because, even if such a principle existed, it could by
definition only be employed within the limits of the treaty in question. In
the view of the Court, Variant C does not meet that cardinal condition
with regard to the 1977 Treaty.
77. As the Court has already observed, the basic characteristic of the
1977 Treaty is, according to Article 1, to provide for the construction of
the Gabcikovo-Nagymaros System of Locks as a joint investment constituting
a single and indivisible operational system of works. This
element is equally reflected in Articles 8 and 10 of the Treaty providing
for joint ownership of the most important works of the GabEikovo-
Nagymaros Project and for the operation of this joint property as a
CO-ordinated single unit. By definition al1 this could not be carried out by unilateral action. In spite of having a certain external physical
similarity with the original Project, Variant C thus differed sharply from
it in its legal characteristics.
78. Moreover, in practice, the operation of Variant C led Czechoslovakia
to appropriate, essentially for its use and benefit, between 80 and
90 per cent of the waters of the Danube before returning them to the
main bed of the river, despite the fact that the Danube is not only a
shared international watercourse but also an international boundary
river.
Czechoslovakia submitted that Variant C was essentially no more than
what Hungary had already agreed to and that the only modifications
made were those which had become necessary by virtue of Hungary's
decision not to implement its treaty obligations. It is true that Hungary,
in concluding the 1977 Treaty, had agreed to the damming of the Danube
and the diversion of its waters into the bypass canal. But it was only in
the context of a joint operation and a sharing of its benefits that Hungary
had given its consent. The suspension and withdrawal of that consent
constituted a violation of Hungary's legal obligations, demonstrating, as
it did, the refusal by Hungary of joint operation; but that cannot mean
that Hungary forfeited its basic right to an equitable and reasonable
sharing of the resources of an international watercourse.
The Court accordingly concludes that Czechoslovakia, in putting
Variant C into operation, was not applying the 1977 Treaty but, on the
contrary, violated certain of its express provisions, and, in so doing,
committed an internationally wrongful act.
79. The Court notes that between November 1991 and October 1992,
Czechoslovakia confined itself to the execution, on its own territory, of
the works which were necessary for the implementation of Variant C, but
which could have been abandoned if an agreement had been reached
between the parties and did not therefore predetermine the final decision
to be taken. For as long as the Danube had not been unilaterally
dammed, Variant C had not in fact been applied.
Such a situation is not unusual in international law or, for that matter,
in domestic law. A wrongful act or offence is frequently preceded by preparatory
actions which are not to be confused with the act or offence
itself. It is as well to distinguish between the actual commission of a
wrongful act (whether instantaneous or continuous) and the conduct
prior to that act which is of a preparatory character and which "does
not qualify as a wrongful act" (see for example the Commentary on
Article 41 of the Draft Articles on State Responsibility, "Report of the
International Law Commission on the work of its forty-eighth session,
6 May-26 July 1996", Officiul Records of the General Assemblj>, Fiftyfirst
Session, Supplemcnt No. 10 (AlSlilO), p. 141, and Yearbook of the
International Law Commission, 1993, Vol. II, Part 2, p. 57, para. 14).

80. Slovakia also maintained that it was acting under a duty to mitigate
damages when it carried out Variant C. It stated that "It is a general
principle of international law that a party injured by the non-performance
of another contract party must seek to mitigate the damage he has
sustained."
It would follow from such a principle that an injured State which has
failed to take the necessary measures to limit the damage sustained would
not be entitled to claim compensation for that damage which could have
been avoided. While this principle might thus provide a basis for the calculation
of damages, it could not, on the other hand, justify an otherwise
wrongful act.
81. Since the Court has found that the putting into operation of Variant
C constituted an internationally wrongful act, the duty to mitigate
damage invoked by Slovakia does not need to be examined further.
82. Although it did not invoke the plea of countermeasures as a
primary argument, since it did not consider Variant C to be unlawful,
Slovakia stated that "Variant C could be presented as a justified
countermeasure to Hungary's illegal acts".
The Court has concluded, in paragraph 78 above, that Czechoslovakia
committed an internationally wrongful act in putting Variant C into
operation. Thus, it now has to determine whether such wrongfulness may
be precluded on the ground that the measure so adopted was in response
to Hungary's prior failure to comply with its obligations under international
law.
83. In order to be justifiable, a countermeasure must meet certain conditions
(see Militurq und Paramilitary Acti~,itie.s in und uguinst Nicaragua
j Nicaraguu v. United Stute~o f Anwrica) , Merits, Judgment, 1. C.J .
Reports 1986. p. 127, para. 249. See also Arbitral Abvard oj 9 Dccrmher
19711 in the case concerning the Air Service Agreement oj 27 Murch 1946
betwern the Unitrd States oj America and France, United Nations,
Reports of lnternutionul Arbitral A)t,ards ( R I A A ) , Vol. XVIII, pp. 443 et
seq.; also Articles 47 to 50 of the Draft Articles on State Responsibility
adopted by the International Law Commission on first reading, "Report
of the International Law Commission on the work of its forty-eighth session,
6 May-26 July 1996", Ofjciul Records of the General Assembly,
Fifty-Jirst Session, Supplement No. 10 (A/51110), pp. 144-145.)
In the first place it must be taken in response to a previous international
wrongful act of another State and must be directed against that
State. Although not primarily presented as a countermeasure, it is clear
that Variant C was a response to Hungary's suspension and abandonment of works and that it was directed against that State; and it is
equally clear, in the Court's view, that Hungary's actions were internationally
wrongful.
84. Secondly, the injured State must have called upon the State committing
the wrongful act to discontinue its wrongful conduct or to make
reparation for it. It is clear from the facts of the case, as recalled above by
the Court (see paragraphs 61 et seq.), that Czechoslovakia requested
Hungary to resume the performance of its treaty obligations on many
occasions.
85. In the view of the Court, an important consideration is that the
effects of a countermeasure must be commensurate with the injury suffered,
taking account of the rights in question.
In 1929, the Permanent Court of International Justice, with regard to
navigation on the River Oder, stated as follows:
"[the] community of interest in a navigable river becomes the basis
of a common legal right, the essential features of which are the perfect
equality of al1 riparian States in the user of the whole course of
the river and the exclusion of any preferential privilege of any one
riparian State in relation to the others" (Territorial Jurisdiction of
the International Commission of the River Oder, Judgment No. 16,
1929, P. C. I. J., Series A, No. 23, p. 27).
Modern development of international law has strengthened this principle
for non-navigational uses of international watercourses as well, as
evidenced by the adoption of the Convention of 21 May 1997 on the Law
of the Non-Navigational Uses of International Watercourses by the
United Nations General Assembly.
The Court considers that Czechoslovakia, by unilaterally assuming
control of a shared resource, and thereby depriving Hungary of its right
to an equitable and reasonable share of the natural resources of the Danube
- with the continuing effects of the diversion of these waters on the
ecology of the riparian area of the Szigetkoz - failed to respect the proportionality
which is required by international law.
86. Moreover, as the Court has already pointed out (see paragraph
78), the fact that Hungary had agreed in the context of the original
Project to the diversion of the Danube (and, in the Joint Contractual
Plan, to a provisional measure of withdrawal of water from the Danube)
cannot be understood as having authorized Czechoslovakia to proceed
with a unilateral diversion of this magnitude without Hungary's consent.
87. The Court thus considers that the diversion of the Danube carried
out by Czechoslovakia was not a lawful countermeasure because it was
not proportionate. It is therefore not required to pass upon one other
condition for the lawfulness of a countermeasure, namely that its purpose
must be to induce the wrongdoing State to comply with its obligations under international law, and that the measure must therefore be
reversible.
88. In the light of the conclusions reached above, the Court, in reply to
the question put to it in Article 2, paragraph 1 (h), of the Special Agreement
(see paragraph 60), finds that Czechoslovakia was entitled to proceed,
in November 1991, to Variant C in so far as it then confined itself
to undertaking works which did not predetermine the final decision to be
taken by it. On the other hand, Czechoslovakia was not entitled to put
that Variant into operation from October 1992.
89. By the terms of Article 2, paragraph 1 (c), of the Special Agreement,
the Court is asked, thirdly, to determine "what are the legal effects
of the notification, on 19 May 1992, of the termination of the Treaty by
the Republic of Hungary".
The Court notes that it has been asked to determine what are the legal
effects of the notification rriven on 19 Mav 1992 of the termination of the G d
Treaty. It will consequently confine itself to replying to this question.
90. The Court will recall that, by early 1992, the respective parties to
the 1977 Treaty had made clear their positions with regard to the recourse
by Czechoslovakia to Variant C. Hungary in a Note Verbale of 14 February
1992 had made clear its view that Variant C was a contravention of
the 1977 Treaty (see paragraph 64 above); Czechoslovakia insisted on the
implementation of Variant C as a condition for further negotiation. On
26 February 1992, in a letter to his Czechoslovak counterpart, the Prime
Minister of Hungary described the impending diversion of the Danube as
"a serious breach of international law" and stated that, unless work was
suspended while further enquiries took place, "the Hungarian Government
[would] have no choice but to respond to this situation of necessity
by terminating the 1977 inter-State Treaty". In a Note Verbale dated
18 March 1992, Czechoslovakia reaffirmed that, while it was prepared to
continue negotiations "on every level", it could not agree "to stop al1
work on the provisional solution".
On 24 March 1992, the Hungarian Parliament passed a resolution
authorizing the Government to terminate the 1977 Treaty if Czechoslovakia
did not stop the works by 30 April 1992. On 13 April 1992, the
Vice-President of the Commission of the European Communities wrote
to both parties confirming the willingness of the Commission to chair a
committee of independent experts including representatives of the two
countries, in order to assist the two ~overnmentsin identifying a mutually acceptable solution. Commission involvement would depend on each
Government not taking "any steps . . . which would prejudice possible
actions to be undertaken on the basis of the report's findings". The
Czechoslovak Prime Minister stated in a letter to the Hungarian Prime
Minister dated 23 April 1992, that his Government continued to be interested
in the establishment of the proposed committee "without any preliminary
conditions"; criticizing Hungary's approach, he refused to suspend
work on the provisional solution, but added, "in my opinion, there
is still time, until the damming of the Danube (Le., until October 31,
1992), for resolving disputed questions on the basis of agreement of both
States".
On 7 May 1992, Hungary, in the very resolution in which it decided on
the termination of the Treaty, made a proposal, this time to the Slovak
Prime Minister, for a six-month suspension of work on Variant C. The
Slovak Prime Minister replied that the Slovak Government remained
ready to negotiate, but considered preconditions "inappropriate".
91. On 19 May 1992, the Hungarian Government transmitted to the
Czechoslovak Government a Declaration notifying it of the termination
by Hungary of the 1977 Treaty as of 25 May 1992. In a letter of the same
date from the Hungarian Prime Minister to the Czechoslovak Prime
Minister, the immediate cause for termination was specified to be Czechoslovakia's
refusal, expressed in its letter of 23 April 1992, to suspend the
work on Variant C during mediation efforts of the Commission of the
European Communities. In its Declaration, Hungary stated that it could
not accept the deleterious effects for the environment and the conservation
of nature of the implementation of Variant C which would be practically
equivalent to the dangers caused by the realization of the original
Project. It added that Variant C infringed numerous international agreements
and violated the territorial integrity of the Hungarian State by
diverting the natural course of the Danube.
92. During the proceedings, Hungary presented five arguments in support
of the lawfulness, and thus the effectiveness, of its notification of
termination. These were the existence of a state of necessity; the impossibility
of performance of the Treaty; the occurrence of a fundamental
change of circumstances; the material breach of the Treaty by Czechoslovakia;
and, finally, the development of new norms of international
environmental law. Slovakia contested each of these grounds.
93. On the first point, Hungary stated that, as Czechoslovakia had
"remained inflexible" and continued with its im~lementationo f Variant
C, "a temporary state of necessity eventually became permanent, justifying
termination of the 1977 Treaty".
Slovakia, for its part, denied that a state of necessity existed on the basis of what it saw as the scientific facts; and argued that even if such a
state of necessity had existed, this would not give rise to a right to terminate
the Treaty under the Vienna Convention of 1969 on the Law of
Treaties.
94. Hungary's second argument relied on the terms of Article 61 of the
Vienna Convention, which is worded as follows:
"Article 61
Supervening Impossibility of' Pe~forrnunce
1. A party may invoke the impossibility of performing a treaty as
a ground for terminating or withdrawing from it if the impossibility
results from the permanent disappearance or destruction of an object
indispensable for the execution of the treaty. If the impossibility is
temporary, it may be invoked only as a ground for suspending the
operation of the treaty.
2. Impossibility of performance may not be invoked by a party as
a ground for terminating, withdrawing from or suspending the operation
of a treaty if the impossibility is the result of a breach by that
party either of an obligation under the treaty or of any other international
obligation owed to any other party to the treaty."
Hungary declared that it could not be "obliged to fulfil a practically
impossible task, namely to construct a barrage system on its own territory
that would cause irreparable environmental damage". It concluded
that
"By May 1992 the essential object of the Treaty - an economic
joint investment which was consistent with environmental protection
and which was operated by the two parties jointly - had permanently
disappeared, and the Treaty had thus become impossible to
perform."
In Hungary's view, the "object indispensable for the execution of the
treaty", whose disappearance or destruction was required by Article 61 of
the Vienna Convention, did not have to be a physical object, but could
also include, in the words of the International Law Commission, "a legal
situation which was the raison d'être of the rights and obligations".
Slovakia claimed that Article 61 was the only basis for invoking impossibility
of performance as a ground for termination, that paragraph 1 of
that Article clearly contemplated physical "disappearance or destruction"
of the object in question, and that, in any event, paragraph 2 precluded
the invocation of impossibility "if the impossibility is the result of a
breach by that party . . . of an obligation under the treaty".
95. As to "fundamental change of circumstances", Hungary relied on
Article 62 of the Vienna Convention on the Law of Treaties which states
as follows:1. A fundamental change of circumstances which has occurred
with regard to those existing at the time of the conclusion of a treaty,
and which was not foreseen by the parties, may not be invoked as a
ground for terminating or withdrawing from the treaty unless:
(a) the existence of those circumstances constituted an essential
basis of the consent of the parties to be bound by the treaty;
and
(h) the effect of the change is radically to transform the extent of
obligations still to be performed under the treaty.
2. A fundamental change of circumstances may not be invoked as
a ground for terminating or withdrawing from a treaty:
( a ) if the treaty establishes a boundary; or
(h) if the fundamental change is the result of a breach by the party
invoking it either of an obligation under the treaty or of any
other international obligation owed to any other party to the
treaty.
3. If, under the foregoing paragraphs, a party may invoke a fundamental
change of circumstances as a ground for terminating or
withdrawing from a treaty it may also invoke the change as a ground
for suspending the operation of the treaty."
Hungary identified a number of "substantive elements" present at the
conclusion of the 1977 Treaty which it said had changed fundamentally
by the date of notification of termination. These included the notion
of "socialist integration", for which the Treaty had originally been a
"vehicle", but which subsequently disappeared; the "single and indivisible
operational system", which was to be replaced by a unilateral scheme;
the fact that the basis of the planned joint investment had been overturned
by the sudden emergence of both States into a market economy;
the attitude of Czechoslovakia which had turned the "framework treaty"
into an "immutable norm"; and, finally, the transformation of a treaty
consistent with environmental protection into "a prescription for environmental
disaster".
Slovakia, for its part, contended that the changes identified by Hungary
had not altered the nature of the obligations under the Treaty from
those originally undertaken, so that no entitlement to terminate it arose
from them.
96. Hungary further argued that termination of the Treaty was justified
by Czechoslovakia's material breaches of the Treaty, and in this
regard it invoked Article 60 of the Vienna Convention on the Law of
Treaties, which provides:"Article 60
Terminution or Suspension of the Operution o f u Treaty
us u Consequence of Its Breach
1. A material breach of a bilateral treaty by one of the parties
entitles the other to invoke the breach as a ground for terminating
the treaty or suspending its operation in whole or in part.
2. A material breach of a multilateral treaty by one of the parties
entitles :
( a ) the other parties by unanimous agreement to suspend the operation
of the treaty in whole or in part or to terminate it either:
(i) in the relations between themselves and the defaulting State,
or
(ii) as between al1 the parties;
( b ) a party specially affected by the breach to invoke it as a ground
for suspending the operation of the treaty in whole or in part in
the relations between itself and the defaulting State;
(c) any party other than the defaulting State to invoke the breach
as a ground for suspending the operation of the treaty in whole
or in part with respect to itself if the treaty is of such a character
that a material breach of its provisions by one party radically
changes the position of every party with respect to the
further performance of its obligations under the treaty.
3. A niaterial breach of a treaty, for the purposes of this article,
consists in:
( a ) a repudiation of the treaty not sanctioned by the present Convention;
or
(6) the violation of a provision essential to the accomplishment of
the object or purpose of the treaty.
4. The foregoing paragraphs are without prejudice to any provision
in the treaty applicable in the event of a breach.
5. Paragraphs 1 to 3 do not apply to provisions relating to the
protection of the human person contained in treaties of a humanitarian
character, in particular to provisions prohibiting any form of
reprisals against perçons protected by such treaties."
Hungary claimed in particular that Czechoslovakia violated the 1977
Treaty by proceeding to the construction and putting into operation of
Variant C, as well as failing to comply with its obligations under Articles
15 and 19 of the Treaty. Hungary further maintained that Czechoslovakia
had breached other international conventions (among them the
Convention of 31 May 1976 on the Regulation of Water Management
Issues of Boundary Waters) and general international law.Slovakia denied that there had been, on the part of Czechoslovakia or
on its part, any material breach of the obligations to protect water quality
and nature, and claimed that Variant C, far from being a breach, was
devised as "the best possible approximate application" of the Treaty. It
furthermore denied that Czechoslovakia had acted in breach of other
international conventions or general international law.
97. Finally, Hungary argued that subsequently imposed requirements
of international law in relation to the protection of the environment precluded
performance of the Treaty. The previously existing obligation not
to cause substantive damage to the territory of another State had, Hungary
claimed, evolved into an ergu omnes obligation of prevention of
damage pursuant to the "precautionary principle". On this basis, Hungary
argued, its termination was "forced by the other party's refusal to
suspend work on Variant Cm.
Slovakia argued, in reply, that none of the intervening developments in
environmental law gave rise to norms of jus cogens that would override
the Treaty. Further, it contended that the claim by Hungary to be
entitled to take action could not in any event serve as legal justification
for termination of the Treaty under the law of treaties, but belonged
rather "to the language of self-help or reprisals".
98. The question, as formulated in Article 2, paragraph 1 ( c ) , of the
Special Agreement, deals with treaty law since the Court is asked to
determine what the legal effects are of the notification of termination of
the Treaty. The question is whether Hungary's notification of 19 May
1992 brought the 1977 Treaty to an end, or whether it did not meet the
requirements of international law, with the consequence that it did not
terminate the Treaty.
99. The Court has referred earlier to the question of the applicability
to the present case of the Vienna Convention of 1969 on the Law of Treaties.
The Vienna Convention is not directly applicable to the 1977 Treaty
inasmuch as both States ratified that Convention only after the Treaty's
conclusion. Consequently only those rules which are declaratory of customary
law are applicable to the 1977 Treaty. As the Court has already
stated above (see paragraph 46), this is the case, in many respects, with
Articles 60 to 62 of the Vienna Convention. relatin"e to termination or
suspension of the operation of a treaty. On this, the Parties, too, were
broadly in agreement.
100. The 1977 Treaty does not contain any provision regarding its termination.
Nor is there any indication that the parties intended to admit
the possibility of denunciation or withdrawal. On the contrary, the
Treaty establishes a long-standing and durable régime of joint investmentand joint operation. Consequently, the parties not having agreed otherwise,
the Treaty could be terminated only on the limited grounds enumerated
in the Vienna Convention.
101. The Court will now turn to the first ground advanced by Hungary,
that of the state of necessity. In this respect, the Court will merely
observe that, even if a state of necessity is found to exist, it is not a
ground for the termination of a treaty. It may only be invoked to exonerate
from its responsibility a State which has failed to implement a
treaty. Even if found justified, it does not terminate a Treaty; the Treaty
may be ineffective as long as the condition of necessity continues to exist ;
it may in fact be dormant, but - unless the parties by mutual agreement
terminate the Treaty - it continues to exist. As soon as the state of
necessity ceases to exist, the duty to comply with treaty obligations
revives.
102. Hungary also relied on the principle of the impossibility of performance
as reflected in Article 61 of the Vienna Convention on the Law
of Treaties. Hungary's interpretation of the wording of Article 61 is,
however, not in conformity with the terms of that Article, nor with the
intentions of the Diplomatic Conference which adopted the Convention.
Article 6 1, paragraph 1, requires the "permanent disappearance or
destruction of an object indispensable for the execution" of the treaty to
justify the termination of a treaty on grounds of impossibility of performance.
During the conference, a proposal was made to extend the scope of
the article by including in it cases such as the impossibility to make certain
payments because of serious financial difficulties (Ojjciul Records of
the United Nations Conjerence on the Luiv qf' Treuties, First Session,
Vienna, 26 Murch-24 Muy 1968, doc. A/CONF.39/11, Summary records
of the plenary meetings and of the meetings of the Committee of the
Whole, 62nd Meeting of the Committee of the Whole, pp. 361-365).
Although it was recognized that such situations could lead to a preclusion
of the wrongfulness of non-performance by a party of its treaty
obligations, the participating States were not prepared to consider such
situations to be a ground for terminating or suspending a treaty,
and preferred to limit themselves to a narrower concept.
103. Hungary contended that the essential object of the Treaty - an
economic joint investment which was consistent with environmental protection
and which was operated by the two contracting parties jointly -
had permanently disappeared and that the Treaty had thus become
impossible to perform. It is not necessary for the Court to determine
whether the term "object" in Article 61 can also be understood to
embrace a legal régime as in any event, even if that were the case, it would have to conclude that in this instance that régime had not definitively
ceased to exist. The 1977 Treaty - and in particular its Articles 15,
19 and 20 - actually made available to the parties the necessary means
to proceed at any time, by negotiation, to the required readjustments
between economic imperatives and ecological imperatives. The Court
would add that, if the joint exploitation of the investment was no longer
possible, this was originally because Hungary did not carry out most of
the works for which it was responsible under the 1977 Treaty; Article 61,
paragraph 2, of the Vienna Convention expressly provides that impossibility
of performance may not be invoked for the termination of a treaty
by a party to that treaty when it results from that party's own breach of
an obligation flowing from that treaty.
104. Hungary further argued that it was entitled to invoke a number
of events which, cumulatively, would have constituted a fundamental
change of circumstances. In this respect it specified profound changes of
a political nature, the Project's diminishing economic viability, the
progress of environmental knowledge and the development of new norms
and prescriptions of international environmental law (see paragraph 95
above).
The Court recalls that, in the Fislzrries Jurisdiction case, it stated that
"Article 62 of the Vienna Convention on the Law of Treaties, . . .
may in many respects be considered as a codification of existing customary
law on the subject of the termination of a treaty relationship
on account of change of circumstances" (I. C. J. Reports 1973, p. 63,
para. 36).
The prevailing political situation was certainly relevant for the conclusion
of the 1977 Treaty. But the Court will recall that the Treaty provided
for a joint investment programme for the production of energy, the control
of floods and the improvement of navigation on the Danube. In the
Court's view, the prevalent political conditions were thus not so closely
linked to the object and purpose of the Treaty that they constituted an
essential basis of the consent of the parties and, in changing, radically
altered the extent of the obligations still to be performed. The same holds
good for the economic system in force at the time of the conclusion of the
1977 Treaty. Besides, even though the estimated profitability of the
Project might have appeared less in 1992 than in 1977, it does not appear
from the record before the Court that it was bound to diminish to such
an extent that the treaty obligations of the parties would have been radically
transformed as a result.
The Court does not consider that new developments in the state of environmental knowledge and of environmental law can be said to
have been completely unforeseen. What is more, the formulation of
Articles 15, 19 and 20, designed to accommodate change, made it possible
for the parties to take account of such developments and to apply
them when implementing those treaty provisions.
The changed circumstances advanced by Hungary are, in the Court's
view, not of such a nature, either individually or collectively, that their
effect would radically transform the extent of the obligations still to be
performed in order to accomplish the Project. A fundamental change of
circumstances must have been unforeseen; the existence of the circumstances
at the time of the Treaty's conclusion must have constituted an
essential basis of the consent of the parties to be bound by the Treaty.
The negative and conditional wording of Article 62 of the Vienna Convention
on the Law of Treaties is a clear indication moreover that the
stability of treaty relations requires that the plea of fundamental change
of circumstances be applied only in exceptional cases.
105. The Court will now examine Hungary's argument that it was
entitled to terminate the 1977 Treaty on the ground that Czechoslovakia
had violated its Articles 15, 19 and 20 (as well as a number of other conventions
and rules of general international law); and that the planning,
construction and putting into operatinn of Variant C also amounted to a
material breach of the 1977 Treatv.
106. As to that part of Hungary's argument which was based on other
treaties and general rules of international law, the Court is of the view
that it is only a material breach of the treaty itself, by a State party to
that treaty, which entitles the other party to rely on it as a ground for
terminating the treaty. The violation of other treaty rules or of rules of
general international law may justify the taking of certain measures,
including countermeasures, by the injured State, but it does not constitute
a ground for termination under the law of treaties.
107. Hungary contended that Czechoslovakia had violated Articles 15,
19 and 20 of the Treaty by refusing to enter into negotiations with Hungary
in order to adapt the Joint Contractual Plan to new scientific and
legal developments regarding the environment. Articles 15, 19 and 20
oblige the parties jointly to take, on a continuous basis, appropriate
measures necessary for the protection of water quality, of nature and of
fishing interests.
Articles 15 and 19 expressly provide that the obligations they contain
shall be implemented by the means specified in the Joint Contractual
Plan. The failure of the parties to agree on those means cannot, on the
basis of the record before the Court, be attributed solely to one party.The Court has not found sufficient evidence to conclude that Czechoslovakia
had consistently refused to consult with Hungary about the desirability
or necessity of measures for the preservation of the environment.
The record rather shows that, while both parties indicated, in principle, a
willingness to undertake further studies, in practice Czechoslovakia
refused to countenance a suspension of the works at Dunakiliti and,
later, on Variant C, while Hungary required suspension as a prior condition
of environmental investigation because it claimed continuation of
the work would prejudice the outcome of negotiations. In this regard it
cannot be left out of consideration that Hungary itself, by suspending the
works at Nagymaros and Dunakiliti, contributed to the creation of a
situation which was not conducive to the conduct of fruitful negotiations.
108. Hungary's main argument for invoking a material breach of the
Treaty was the construction and putting into operation of Variant C. As
the Court has found in paragraph 79 above, Czechoslovakia violated the
Treaty only when it diverted the waters of the Danube into the bypass
canal in October 1992. In constructing the works which would lead to
the putting into operation of Variant C, Czechoslovakia did not act
unlawfully.
In the Court's view, therefore, the notification of termination by Hungary
on 19 May 1992 was premature. No breach of the Treaty by
Czechoslovakia had yet taken place and consequently Hungary was not
entitled to invoke any such breach of the Treaty as a ground for terminating
it when it did.
-109. In this regard, it should be noted that, according to Hungary's
Declaration of 19 May 1992, the termination of the 1977 Treaty was to
take effect as from 25 May 1992, that is only six days later. Both Parties
agree that Articles 65 to 67 of the Vienna Convention on the Law of
Treaties, if not codifying customary law, at least generally reflect customary
international law and contain certain procedural principles which are
based on an obligation to act in good faith. As the Court stated in its
Advisory Opinion on the Interpretufion of tlze Agreement of 25 March
1951 hetiilren tlze WHO und Egypt (in which case the Vienna Convention
did not apply) :
"Precisely what periods of time may be involved in the observance
of the duties to consult and negotiate, and what period of notice of
termination should be given, are matters which necessarily Vary
according to the requirements of the particular case. In principle,
therefore, it is for the parties in each case to determine the length of
those periods by consultation and negotiation in good faith." (1. C. J.
Reports 1980, p. 96, para. 49.)
The termination of the Treaty by Hungary was to take effect six days after its notification. On neither of these dates had Hungary suffered
injury resulting from acts of Czechoslovakia. The Court must therefore
confirm its conclusion that Hungary's termination of the Treaty was
premature.
110. Nor can the Court overlook that Czechoslovakia committed the
internationally wrongful act of putting into operation Variant C as a
result of Hungary's own prior wrongful conduct. As was stated by the
Permanent Court of International Justice:
"It is, moreover, a principle generally accepted in the jurisprudence
of international arbitration, as well as by municipal courts,
that one Party cannot avail himself of the fact that the other has not
fulfilled some obligation or has not had recourse to some means of
redress, if the former Party has, by some illegal act, prevented the
latter from fulfilling the obligation in question, or from having
recourse to the tribunal which would have been open to him." (Fuctory
at Chorzo~v, Jurisdiction, Juclgment No. 8, 1927, P. C. I. J..
Series A, No. 9, p. 3 1 .)
Hungary, by its own conduct, had prejudiced its right to terminate the
Treaty; this would still have been the case even if Czechoslovakia, by the
time of the purported termination, had violated a provision essential to
the accomplishment of the object or purpose of the Treaty.
11 1. Finally, the Court will address Hungary's claim that it was
entitled to terminate the 1977 Treaty because new requirements of international
law for the protection of the environment precluded performance
of the Treaty.
112. Neither of the Parties contended that new DeremDtorv norms of
environmental law had emerged since the conclusion of tke 1677 Treaty,
and the Court will consequently not be required to examine the scope of
Article 64 of the Vienna Convention on the Law of Treaties. On the other
hand, the Court wishes to point out that newly developed norms of environmental
law are relevant for the implementation of the Treaty and that
the parties could, by agreement, incorporate them through the application
of Articles 15, 19 and 20 of the Treaty. These articles do not contain
specific obligations of performance but require the parties, in carrying
out their obligations to ensure that the quality of water in the Danube is
not impaired and that nature is protected, to take new environmental
norms into consideration when agreeing upon the means to be specified
in the Joint Contractual Plan.
By inserting these evolving provisions in the Treaty, the parties recognized
the potential necessity to adapt the Project. Consequently, the Treaty is not static, and is open to adapt to emerging norms of international
law. By means of Articles 15 and 19, new environmental norms can
be incorporated in the Joint Contractual Plan.
The responsibility to do this was a joint responsibility. The obligations
contained in Articles 15, 19 and 20 are, by definition, general and have to
be transformed into specific obligations of performance through a process
of consultation and negotiation. Their implementation thus requires
a mutual willingness to discuss in good faith actual and potential environmental
risks.
It is al1 the more important to do this because as the Court recalled in
its Advisory Opinion on the Legulity of the Threut or Use of Nucleur
Weupons, "the environment is not an abstraction but represents the living
space, the quality of life and the very health of human beings, including
generations unborn" ( I . C.J. Reports 1996, p. 241, para. 29; see also paragraph
53 above).
The awareness of the vulnerability of the environment and the recognition
that environmental risks haveto be assessed on a continuous basis
have become much stronger in the years since the Treaty's conclusion.
These new concerns have enhanced the relevance of Articles 15, 19
and 20.
113. The Court recognizes that both Parties agree on the need to take
environmental concerns seriously and to take the required precautionary
measures, but they fundamentally disagree on the consequences this has
for the joint Project. In such a case, third-party involvement may be helpful
and instrumental in finding a solution, provided each of the Parties is
flexible in its position.
114. Finally, Hungary maintained that by their conduct both parties
had repudiated the Treaty and that a bilateral treaty repudiated by both
parties cannot survive. The Court is of the view, however, that although
it has found that both Hungary and Czechoslovakia failed to comply
with their obligations under the 1977 Treaty, this reciprocal wrongful
conduct did not bring the Treaty to an end nor justify its termination.
The Court would set a precedent with disturbing implications for treaty
relations and the integrity of the rule puctu sunt servunda if it were to
conclude that a treaty in force between States, which the parties have
implemented in considerable measure and at great cost over a period of
years, might be unilaterally set aside on grounds of reciprocal noncompliance.
It would be otherwise, of course, if the parties decided to
terminate the Treaty by mutual consent. But in this case, while Hungary
purported to terminate the Treaty, Czechoslovakia consistently resisted
this act and declared it to be without legal effect. 1 15. In the light of the conclusions it has reached above, the Court, in
reply to the question put to it in Article 2, paragraph 1 (c), of the Special
Agreement (see paragraph 89), finds that the notification of termination
by Hungary of 19 May 1992 did not have the legal effect of terminating
the 1977 Treaty and related instruments.
116. In Article 2, paragraph 2, of the Special Agreement, the Court is
requested to determine the legal consequences, including the rights and
obligations for the Parties, arising from its Judgment on the questions
formulated in paragraph 1. In Article 5 of the Special Agreement the
Parties agreed to enter into negotiations on the modalities for the execution
of the Judgment immediately after the Court has rendered it.
117. The Court must first turn to the question whether Slovakia
became a party to the 1977 Treaty as successoi to Czechoslovakia. As an
alternative argument, Hungary contended that, even if the Treaty survived
the notification of termination, in any event it ceased to be in force
as a treaty on 31 December 1992, as a result of the "disappearance of one
of the parties". On that date Czechoslovakia ceased to exist as a legal
entity, and on 1 January 1993 the Czech Republic and the Slovak Republic
came into existence.
118. According to Hungary, "There is no rule of international law
which provides for automatic succession to bilateral treaties on the disappearance
of a party" and such a treaty will not survive unless another
State succeeds to it by express agreement between that State and the
remaining party. While the second paragraph of the Preamble to the
Special Agreement recites that
"the Slovak Republic is one of the two successor States of the Czech
and Slovak Federal Republic and the sole successor State in respect
of rights and obligations relating to the Gabtikovo-Nagymaros
Project",
Hungary sought to distinguish between, on the one hand, rights and obligations
such as "continuing property rights" under the 1977 Treaty, and,
on the other hand, the treaty itself. It argued that, during the negotiations
leading to signature of the Special Agreement, Slovakia had proposed a
text in which it would have been expressly recognized "as the successor to
the Government of the CSFR" with regard to the 1977 Treaty, but that
Hungary had rejected that formulation. It contended that it had never
agreed to accept Slovakia as successor to the 1977 Treaty. Hungary
referred to diplomatic exchanges in which the two Parties had each submitted
to the other lists of those bilateral treaties which they respectively
wished should continue in force between them. for negotiation on a case by-case basis; and Hungary emphasized that no agreement was ever
reached with regard to the 1977 Treaty.
119. Hungary claimed that tbere was no rule of succession which
could operate in the present case to override the absence of consent.
Referring to Article 34 of the Vienna Convention of 23 August 1978 on
Succession of States in respect of Treaties, in which "a rule of automatic
succession to al1 treaties is provided for", based on the principle of continuity,
Hungary argued not only that it never signed or ratified the Convention,
but that the "concept of automatic succession" contained in that
Article was not and is not, and has never been accepted as, a statement of
general international 1aw.
Hungary further submitted that the 1977 Treaty did not create "obligations
and rights . . . relating to the régime of a boundary" within the
meaning of Article II of that Convention, and noted that the existing
course of the boundary was unaffected by the Treaty. It also denied that
the Treaty was a "localized" treaty, or that it created rights "considered
as attaching to [the] territory" within the meaning of Article 12 of the
1978 Convention, which would, as such, be unaffected by a succession of
States. The 1977 Treaty was, Hungary insisted, simply a joint investment.
Hungary's conclusion was that there is no basis on which the Treaty
could have survived the disappearance of Czechoslovakia so as to be
binding as between itself and Slovakia.
120. According to Slovakia, the 1977 Treaty, which was not lawfully
terminated by Hungary's notification in May 1992, remains in force
between itself, as successor State, and Hungary.
Slovakia acknowledged that there was no agreement on succession to
the Treaty between itself and Hungary. It relied instead, in the first place,
on the "general rule of continuity which applies in the case of dissolution";
it argued, secondly, that the Treaty is one "attaching to [the] territory"
within the meaning of Article 12 of the 1978 Vienna Convention,
and that it contains provisions relating to a boundary.
121. In support of its first argument Slovakia cited Article 34 of the
1978 Vienna Convention, which it claimed is a statement of customary
international law, and which imposes the principle of automatic succession
as the rule applicable in the case of dissolution of a State where the
~redecessor State has ceased to exist. Slovakia maintained that State
practice in cases of dissolution tends to support continuity as the rule to
be followed with regard to bilateral treaties. Slovakia having succeeded
to part of the territory of the former Czechoslovakia, this would be the
rule applicable in the present case.
122. Slovakia's second argument rests on "the principle of ipso jure
continuity of treaties of a territorial or localized character". This rule,
Slovakia said, is embodied in Article 12 of the 1978 Convention, which in
part provides as follows : "Article 12
Other Territorial Regimes
. . . . . . . . . . . . . . . . . . . . . . . .
2. A succession of States does not as such affect:
(a) obligations relating to the use of any territory, or to restrictions
upon its use, established by a treaty for the benefit of a group of
States or of al1 States and considered as attaching to that territory;
( h ) rights established by a treaty for the benefit of a group of States
or of al1 States and relating to the use of any territory, or to
restrictions upon its use, and considered as attaching to that
territory."
According to Slovakia, "[this] article [too] can be considered to be one
of those provisions of the Vienna Convention that represent the codification
of customary international law". The 1977 Treaty is said to fall
within its scoDe because of its "suecific characteristics . . . which ulace it
in the category of treaties of a localized or territorial character". Slovakia
also described the Treaty as one "which contains boundary provisions
and lays down a specific territorial régime" which operates in the interest
of al1 Danube riparian States, and as "a dispositive treaty, creating rights
in rem, independently of the legal personality of its original signatories".
Here, Slovakia relied on the recognition by the International Law Commission
of the existence of a "special rule" whereby treaties "intended to
establish an objective régime" must be considered as binding on a successor
State (OfJicial Records of the United Nations Conferencc on the
Succession ofStutes in respect of Treaties, Vol. I I I , doc. AICONF.80I16I
Add.2, p. 34). Thus, in Slovakia's view, the 1977 Treaty was not one
which could have been terminated through the disappearance of one of
the original parties.
123. The Court does not find it necessary for the purposes of the
present case to enter into a discussion of whether or not Article 34 of the
1978 Convention reflects the state of customary international law. More
relevant to its present analysis is the particular nature and character of
the 1977 Treaty. An examination of this Treaty confirms that, aside from
its undoubted nature as a joint investment, its major elements were the
proposed construction and joint operation of a large, integrated and indivisible
complex of structures and installations on specific parts of the
respective territories of Hungary and Czechoslovakia along the Danube.
The Treaty also established the navigational régime for an important sector
of an international waterway, in particular the relocation of the main
international shipping lane to the bypass canal. In so doing, it inescapably
created a situation in which the interests of other users of the Dan ube were affected. Furthermore, the interests of third States were expressly
acknowledged in Article 18, whereby the parties undertook to ensure
"uninterrupted and safe navigation on the international fairway" in
accordance with their obligations under the Convention of 18 August
1948 concerning the Régime of Navigation on the Danube.
In its Commentary on the Draft Articles on Succession of States in
respect of Treaties, adopted at its twenty-sixth session, the International
Law Commission identified "treaties of a territorial character" as having
been regarded both in traditional doctrine and in modern opinion as unaffected
by a succession of States (OfJicial Records of the United Nations
Conference on the Succession of States in respect of Treaties, Vol. III,
doc. A/CONF.80/16/Add.2, p. 27, para. 2). The draft text of Article 12,
which reflects this principle, was subsequently adopted unchanged in the
1978 Vienna Convention. The Court considers that Article 12 reflects a
rule of customary international law; it notes that neither of the Parties
disputed this. Moreover, the Commission indicated that "treaties concerning
water rights or navigation on rivers are commonly regarded as
candidates for inclusion in the category of territorial treaties" (ibid.,
p. 33, para. 26). The Court observes that Article 12, in providing only,
without reference to the treaty itself, that rights and obligations of a territorial
character established by a treaty are unaffected by a succession of
States, appears to lend support to the position of Hungary rather than of
Slovakia. However the Court concludes that this formulation was devised
rather to take account of the fact that, in many cases, treaties which had
established boundaries or territorial régimes were no longer in force
(ibid, pp. 26-37). Those that remained in force would nonetheless bind a
successor State.
Taking al1 these factors into account, the Court finds that the content
of the 1977 Treaty indicates that it must be regarded as establishing a
territorial régime within the meaning of Article 12 of the 1978 Vienna
Convention. It created rights and obligations "attaching tom the parts of
the Danube to which it relates; thus the Treaty itself cannot be affected
by a succession of States. The Court therefore concludes that the 1977
Treaty became binding upon Slovakia on 1 January 1993.
124. It might be added that Slovakia also contended that, while still a
constituent part of Czechoslovakia, it played a role in the development of
the Project, as it did later, in the most critical phase of negotiations with
Hungary about the fate of the Project. The evidence shows that the Slovak
Government passed resolutions prior to the signing of the 1977
Treaty in preparation for its implementation; and again, after signature,
expressing its support for the Treaty. It was the Slovak Prime Minister
who attended the meeting held in Budapest on 22 April 199 1 as the Plenipotentiary
of the Federal Government to discuss questions arising out of
the Project. It was his successor as Prime Minister who notified his Hungarian counterpart by letter on 30 July 1991 of the decision of the Government
of the Slovak Republic, as well as of the Government of the
Czech and Slovak Federal Republic, to proceed with the "provisional
solution" (see paragraph 63 above); and who wrote again on 18 December
1991 to the Hungarian Minister without Portfolio, renewing an
earlier suggestion that a joint commission be set up under the auspices of
the European Communities to consider possible solutions. The Slovak
Prime Minister also wrote to the Hungarian Prime Minister in May 1992
on the subject of the decision taken by the Hungarian Government to
terminate the Treaty, informing him of resolutions passed by the Slovak
Government in response.
It is not necessary, in the light of the conclusions reached in paragraph
123 above, for the Court to determine whether there are legal consequences
to be drawn from the prominent part thus played by the Slovak
Republic. Its role does, however, deserve mention.
125. The Court now turns to the other legal consequences arising from
its Judgment.
As to this, Hungary argued that future relations between the Parties, as
far as Variant C is concerned, are not governed by the 1977 Treaty. It
claims that it is entitled, pursuant to the Convention of 1976 on the
Regulation of Water Management Issues of Boundary Waters, to "50%
of the natural flow of the Danube at the point at which it crosses the
boundary below ~unovo"a nd considers that the Parties
"are obliged to enter into negotiations in order to produce the result
that the water conditions along the area from below Cunovo to
below the confluence at Sap become jointly defined water conditions
as required by Article 3 (u) of the 1976 Convention".
Hungary moreover indicated that any mutually accepted long-term discharge
régime must be "capable of avoiding damage, including especially
damage to biodiversity prohibited by the [1992 Rio Convention on Biological
Diversity]". It added that "a joint environmental impact assessment
of the region and of the future of Variant C structures in the context
of the sustainable development of the region" should be carried out.
126. Hungary also raised the question of financial accountability for
the failure of the original project and stated that both Parties accept the
fact that the other has "proprietary and financial interests in the residues
of the original Project and that an accounting has to be carried out".
Furthermore, it noted that:
"Other elements of damage associated with Variant C on Hungarian
territory also have to be brought into the accounting . . ., as well
as electricity production since the diversion",and that: "The overall situation is a complex one, and it may be most
easily resolved by some form of lump sum settlement."
127. Hungary stated that Slovakia had incurred international responsibility
and should make reparation for the damage caused to Hungary
by the operation of Variant C. In that connection, it referred, in the context
of reparation of the damage to the environment, to the rule of restitutio
in integrum, and called for the re-establishment of "joint control
by the two States over the installations maintained as they are now", and
the "re-establishment of the flow of [the] waters to the level at which it
stood prior to the unlawful diversion of the river". It also referred to
reparation of the damage to the fauna, the flora, the soil, the sub-soil, the
groundwater and the aquifer, the damages suffered by the Hungarian
population on account of the increase in the uncertainties weighing on its
future (pretium doloris), and the damage arising from the unlawful use,
in order to divert the Danube, of installations over which the two Parties
exercised joint ownership.
Lastly, Hungary called for the "cessation of the continuous unlawful
acts" and a "guarantee that the same actions will not be repeated", and
asked the Court to order "the permanent suspension of the operation of
Variant Cm.
128. Slovakia argued for its part that Hungary should put an end to its
unlawful conduct and cease to impede the application of the 1977 Treaty,
taking account of its "flexibility and of the important possibilities of
development for which it provides, or even of such amendments as might
be made to it by agreement between the Parties, further to future negotiations".
It stated that joint operations could resume on a basis jointly
agreed upon and emphasized the following:
"whether Nagymaros is built as originally planned, or built elsewhere
in a different form, or, indeed, not built at all, is a question to
be decided by the Parties some time in the future.
Provided the bypass canal and the Gabtikovo Power-station and
Locks - both part of the original Treaty, and not part of Variant C
- remain operational and economically viable and efficient, Slovakia
is prepared to negotiate over the future roles of Dunakiliti
and Cunovo, bearing Nagymaros in mind."
It indicated that the Gabtikovo power plant would not operate in peak
mode "if the evidence of environmental damage [was] clear and accepted
by both Parties". Slovakia noted that the Parties appeared to agree that
an accounting should be undertaken "so that, guided by the Court's findings
on responsibility, the Parties can try to reach a global settlement". It added that the Parties would have to agree on how the sums due are to be
paid.
129. Slovakia stated that Hungary must make reparation for the
deleterious consequences of its failures to comply with its obligations,
"whether they relate to its unlawful suspensions and abandonments of
works or to its formal repudiation of the Treaty as from May 1992", and
that compensation should take the form of a rrstitutio in integrum. It
indicated that "Unless the Parties come to some other arrangement by
concluding an agreement, restitutio in integrurn ought to take the form of
a return by Hungary, ut a future tirne, to its obligations under the
Treaty" and that "For compensation to be 'full' . . ., to 'wipe out al1 the
consequences of the illegal act' . . ., a payment of compensation must . . .
be added to the rcstitutio . . ." Slovakia claims compensation which must
include both interest and loss of profits and should cover the following
heads of damage, which it offers by way of guidance:
(1) Losses caused to Slovakia in the GabCikovo sector: costs incurred
from 1990 to 1992 by Czechoslovakia in protecting the structures of
the GIN project and adjacent areas; the cost of maintaining the old
bed of the River Danube pending the availability of the new navigation
canal, from 1990 to 1992; losses to the Czechoslovak navigation
authorities due to the unavailability of the bypass canal from 1990 to
1992 ; construction costs of Variant C (1 990- 1992).
(2) Losses caused to Slovakia in the Nagymaros sector: losses in the field
of navigation and flood protection incurred since 1992 by Slovakia
due to the failure of Hungary to proceed with the works.
(3) Loss of electricity production.
Slovakia also calls for Hungary to "give the appropriate guarantees
that it will abstain from preventing the application of the Treaty and the
continuous operation of the system". It argued from that standpoint that
it is entitled "to be given a formal assurance that the internationally
wrongful acts of Hungary will not recur':, and it added that "the maintenance
of the closure of the Danube at Cunovo constitutes a guarantee
of that kind", unless Hungary gives an equivalent guarantee "within the
framework of the negotiations that are to take place between the Parties".
130. The Court observes that the part of its Judgment which answers
the questions in Article 2, paragraph 1, of the Special Agreement has a
declaratory character. 1t deals with the past conduct of the Parties and
determines the lawfulness or unlawfulness of that conduct between 1989
and 1992 as well as its effects on the existence of the Treaty.
131. Now the Court has, on the basis of the foregoing findings, to determine what the future conduct of the Parties should be. This part of
the Judgment is prescriptive rather than declaratory because it determines
what the rights and obligations of the Parties are. The Parties will
have to seek agreement on the modalities of the execution of the Judgment
in the light of this determination, as they agreed to do in Article 5
of the Special Agreement.
132. In this regard it is of cardinal importance that the Court has
found that the 1977 Treaty is still in force and consequently governs the
relationship between the Parties. That relationship is also determined by
the rules of other relevant conventions to which the two States are party,
by the rules of general international law and, in this particular case, by
the rules of State responsibility; but it is governed, above all, by the
applicable rules of the 1977 Treaty as a les speciulis.
133. The Court, however, cannot disregard the fact that the Treaty has
not been fully implemented by either party for years, and indeed that
their acts of commission and omission have contributed to creating the
factual situation that now exists. Nor can it overlook that factual situation
- or the practical possibilities and impossibilities to which it gives
rise - when deciding on the legal requirements for the future conduct of
the Parties.
This does not mean that facts - in this case facts which flow from
wrongful conduct - determine the law. The principle e.u injuria jus non
oritur is sustained by the Court's finding that the legal relationship
created by the 1977 Treaty is preserved and cannot in this case be treated
as voided by unlawful conduct.
What is essential, therefore, is that the factual situation as it has developed
since 1989 shall be placed within the context of the preserved and
developing treaty relationship, in order to achieve its object and purpose
in so far as that is feasible. For it is only then that the irregular state of
affairs which exists as the result of the failure of both Parties to comply
with their treaty obligations can be remedied.
134. What might have been a correct application of the law in 1989 or
1992, if the case had been before the Court then, could be a miscarriage
of justice if prescribed in 1997. The Court cannot ignore the fact that the
GabEikovo power plant has bpen in operation for nearly five years, that
the bypass canal which feeds the plant receives its water from a significantly
smaller reservoir formed by a dam which is built not at Dunakiliti
but at Cunovo, and that the plant is operated in a run-of-the-river mode
and not in a peak hour mode as originally foreseen. Equally, the Court
cannot ignore the fact that, not only has Nagymaros not been built, but
that, with the effective discarding by both Parties of peak power operation,
there is no longer any point in building it.
135. As the Court has already had occasion to point out, the 1977
Treaty was not only a joint investment project for the production of energy, but it was designed to serve other objectives as well: the improvement
of the navigability of the Danube, flood control and regulation of
ice-discharge, and the protection of the natural environment. None of
these objectives has been given absolute priority over the other, in spite
of the emphasis which is given in the Treaty to the construction of a
System of Locks for the production of energy. None of them has lost its
importance. In order to achieve these objectives the parties accepted obligations
of conduct, obligations of performance, and obligations of result.
136. It could be said that that part of the obligations of performance
which related to the construction of the System of Locks - in so far as
they were not yet implemented before 1992 - have been overtaken by
events. It would be an administration of the law altogether out of touch
with reality if the Court were to order those obligations to be fully reinstated
and the works at Cunovo to be demolished when the objectives
of the Treaty can be adequately served by the existing structures.
137. Whether this is indeed the case is, first and foremost, for the
Parties to decide. Under the 1977 Treaty ils several objectives must be
attained in an integrated and consolidated programme, to be developed
in the Joint Contractual Plan. The Joint Contractual Plan was, until
1989, adapted and amended frequently to better fit the wishes of the
parties. This Plan was also expressly described as the means to achieve
the objectives of maintenance of water quality and protection of the environment.
138. The 1977 Treaty never laid down a rigid system, albeit that the
construction of a system of locks at GabEikovo and Nagymaros was prescribed
by the Treaty itself. In this respect, however, the subsequent positions
adopted by the parties should be taken into consideration. Not only
did Hungary insist on terminating construction at Nagymaros, but
Czechoslovakia stated, on various occasions in the course of negotiations,
that it was willing to consider a limitation or even exclusion of
operation in peak hour mode. In the latter case the construction of the
Nagymaros dam would have become pointless. The explicit terms of the
Treaty itself were therefore in practice acknowledged by the parties to be
negotiable.
139. The Court is of the opinion that the Parties are under a legal obligation,
during the negotiations to be held by virtue of Article 5 of the
Special Agreement, to consider, within the context of the 1977 Treaty, in
what way the multiple objectives of the Treaty can best be served, keeping
in mind that al1 of them should be fulfilled.
140. It is clear that the Project's impact upon, and its implications for,
the environment are of necessity a key issue. The numerous scientific
reports which have been presented to the Court by the Parties - even if
their conclusions are often contradictory - provide abundant evidence
that this impact and these implications are considerable.
In order to evaluate the environmental risks, current standards must be
taken into consideration. This is not only allowed by the wording of Articles 15 and 19, but even prescribed, to the extent that these
articles impose a continuing - and thus necessarily evolving - obligation
on the parties to maintain the quality of the water of the Danube
and to protect nature.
The Court is mindful that, in the field of environmental protection,
vigilance and prevention are required on account of the often irreversible
character of damage to the environment and of the limitations inherent
in the very mechanism of reparation of this type of damage.
Throughout the ages, mankind has, for economic and other reasons,
constantly interfered with nature. In the past, this was often done without
consideration of the effects upon the environment. Owing to new
scieritific insights and to a growing awareness of the risks for mankind -
for present and future generations - of pursuit of such interventions at
an unconsidered and unabated pace, new norms and standards have been
developed, set forth in a great number of instruments during the last two
decades. Such new norms have to be taken into consideration, and such
new standards given proper weight, not only when States contemplate
new activities but also when continuing with activities begun in the past.
This need to reconcile economic development with protection of the environment
is aptly expressed in the concept of sustainable development.
For the purposes of the present case, this means that the Parties
together should look afresh at the effects on the environment of the
operation of the GabCikovo power plant. In particular they must find a
satisfactory solution for the volume of water to be released into the old
bed of the Danube and into the side-arms on both sides of the river.
141. It is not for the Court to determine what shall be the final result
of these negotiations to be conducted by the Parties. It is for the Parties
themselves to find an agreed solution that takes account of the objectives
of the Treaty, which must be pursued in a joint and integrated way, as
well as the norms of international environmental law and the principles
of the law of international watercourses. The Court will recall in this context
that, as it said in the North Seu Continental Shelfcases:
"[the Parties] are under an obligation so to conduct themselves that
the negotiations are meaningful, which will not be the case when
either of them insists upon its own position without contemplating
any modification of it" (I.C.J. Reports 1969, p. 47, para. 85).
142. What is required in the present case by the rule puctu sunt servanda,
as reflected in Article 26 of the Vienna Convention of 1969 on the
Law of Treaties, is that the Parties find an agreed solution within the cooperative
context of the Treaty.
Article 26 combines two elements, which are of equal importance. It
provides that "Every treaty in force is binding upon the parties to it and must be performed by them in good faith." This latter element, in the
Court's view, implies that, in this case, it is the purpose of the Treaty, and
the intentions of the parties in concluding it, which should prevail over
its literal application. The principle of good faith obliges the Parties to
apply it in a reasonable way and in such a manner that its purpose can be
realized.
143. During this dispute both Parties have called upon the assistance
of the Commission of the European Communities. Because of the diametrically
opposed positions the Parties took with regard to the required
outcome of the trilateral talks which were envisaged, those talks did not
succeed. When, after the present Judgment is given, bilateral negotiations
without pre-conditions are held, both Parties can profit from the assistance
and expertise of a third party. The readiness of the Parties to accept
such assistance would be evidence of the good faith with which they conduct
bilateral negotiations in order to give effect to the Judgment of the
Court.
144. The 1977 Treaty not only contains a joint investment programme,
it also establishes a régime. According to the Treaty, the main structures
of the System of Locks are the joint property of the Parties; their operation
will take the form of a co-ordinated single unit; and the benefits of
the project shall be equally shared.
Since the Court has found that the Treaty is still in force and that,
under its terms, the joint régime is a basic element, it considers that,
unless the Parties agree otherwise, such a régime should be restored.
145. Article 10, paragraph 1, of the Treaty states that works of the
System of Locks constituting the joint property of the contracting parties
shall be operated, as a co-ordinated single unit and in accordance with
jointly agreed operating and operational procedures, by the authorized
operating agency of the contracting party in whose territory the works
are built. Paragraph 2 of that Article states that works on the System of
Locks owned by one of the contracting parties shall be independently
operated or maintained by the agencies of that contracting party in the
jointly prescribed manner.
The Court is of the opinion that the works at ~ u n o v osh ould become
a jointly operated unit within the meaning of Article 10, paragraph 1, in
view of their pivotal role in the operation of what rem+ of the Project
and for the water-management régime. The dam at Cunovo has taken
over the role which was originally destined for the works at Dunakiliti,
and therefore should have a similar status.
146. The Court also concludes that Variant C, which it considers operates
in a manner incompatible with the Treaty, should be made to conform
to it. By associating Hungary, on an equal footing, in its operation,
management and benefits, Variant C will be transformed from a de facto
status into a treaty-based régime.
It appears from various parts of the record that, given the current state

151. The Court has been asked by both Parties to determine the consequences
of the Judgment as they bear upon payment of damages.
According to the Preamble to the Special Agreement, the Parties agreed
that Slovakia is the sole successor State of Czechoslovakia in respect of
rights and obligations relating to the GabCikovo-Nagymaros Project.
Slovakia thus may be liable to pay compensation not only for its own
wrongful conduct but also for that of Czechoslovakia, and it is entitled to
be compensated for the damage sustained by Czechoslovakia as well as
by itself as a result of the wrongful conduct of Hungary.
152. The Court has not been asked at this stage to determine the quantum
of damages due, but to indicate on what basis they should be paid.
Both Parties claimed to have suffered considerable financial losses and
both claim pecuniary compensation for them.
It is a well-established rule of international law that an injured State is
entitled to obtain compensation from the State which has committed an
internationally wrongful act for the damage caused by it. In the present
Judgment, the Court has concluded that both Parties committed internationally
wrongful acts, and it has noted that those acts gave rise to the
damage sustained by the Parties; consequently, Hungary and Slovakia
are both under an obligation to pay compensation and are both entitled
to obtain compensation.
Slovakia is accordingly entitled to compensation for the damage suffered
by Czechoslovakia as well as by itself as a result of Hungary's decision
to suspend and subsequently abandon the works at Nagymaros and
Dunakiliti, as those actions caused the postponement of the putting into
operation of the GabCikovo power plant, and changes in its mode of
operation once in service.
Hungary is entitled to compensation for the damage sustained as a
result of the diversion of the Danube, since Czechoslovakia, by putting
into operation Variant C, and Slovakia, in maintaining it in service,
deprived Hungary of its rightful part in the shared water resources, and
exploited those resources essentially for their own benefit.
153. Given the fact, however, that there have been intersecting wrongs
by both Parties, the Court wishes to observe that the issue of compensation
could satisfactorily be resolved in the framework of an overall
settlement if each of the Parties were to renounce or cancel al1 financial
claims and counter-claims.
154. At the same time, the Court wishes to point out that the settlement
of accounts for the construction of the works is different from the
issue of compensation, and must be resolved in accordance with the 1977
Treaty and related :instruments. If Hungary is to share in the operation
and benefits of the Cunovo complex, it must pay a proportionate share of
the building and running costs.

155. For these reasons,
the court,
(1) Having regard to Article 2, paragraph 1, of the Special Agreement,
A. By fourteen votes to one,
Finds that Hungary was not entitled to suspend and subsequently
abandon, in 1989, the works on the Nagymaros Project and on the
part of the GabCikovo Project for which the Treaty of 16 September
1977 and related instruments attributed responsibility to it;
IN FAVOUK : Pre.~ident Schwebel; Vice-Prrsident Weeramantry ; Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi, Fleischhauer, Koroma,
Vereshchetin, Parra-Aranguren, Kooijmans, Rezek; Judge ad hoc
Skubiszewski ;
AGAINSJTud: ge Herczegh;
B. By nine votes to six,
Finds that Czechoslovakia was entitled to proceed, in November
1991, to the "provisional solution" as described in the terms of the
Special Agreement ;
IN FAVOUR : Vice-President Weeramantry ; Judges Oda, Guillaume, Shi,
Koroma, Vereshchetin, Parra-Aranguren, Kooijmans; Judge ad hoc
Skubiszewski ;
AGAINST : President Schwebel ; Judges Bedjaoui, Ranjeva, Herczegh,
Fleischhauer, Rezek;
C. By ten votes to five,
Finds that Czechoslovakia was not entitled to put into operation,
from October 1992, this "provisional solution";
IN FAVOUR : President Schwebel ; Vice-President Weeramantry ; Judges
Bedjaoui, Guillaume, Ranjeva, Herczegh, Shi, Fleischhauer, Kooijmans,
Rezek;
AGAINSJTu:d ges Oda, Koroma, Vereshchetin, Parra-Aranguren; Judge
ad hoc Skubiszewski;
D. By eleven votes to four,
Finds that the notification, on 19 May 1992, of the termination of
the Treaty of 16 September 1977 and related instruments by Hungary
did not have the legal effect of terminating them;
IN FAVOURV: ice-Pre~ident Weeramantry; Judges Oda, Bedjaoui,
Guillaume, Ranjeva, Shi, Koroma, Vereshchetin, Parra-Aranguren,
Kooijmans; Judge ad hoc Skubiszewski;
AGAINST : President Schwebel ; Judgrs Herczegh, Fleischhauer, Rezek ;

2) Having regard to Article 2, paragraph 2, and Article 5 of the Special
Agreement,
A. By twelve votes to three,
Finds that Slovakia, as successor to Czechoslovakia, became a
party to the Treaty of 16 September 1977 as from 1 January 1993;
IN FAVOUR : President Schwebel ; Vice- President Weeramantry ; Judges
Oda, Bedjaoui, Guillaume, Ranjeva. Shi, Koroma, Vereshchetin,
Parra-Aranguren, Kooijmans: Judge ad hoc Skubiszewski;
AGAINSJTud: ges Herczegh, Fleischhauer, Rezek ;
B. By thirteen votes to two,
Finds that Hungary and Slovakia must negotiate in good faith in
the light of the prevailing situation, and must take al1 necessary measures
to ensure the achievement of the objectives of the Treaty of
16 September 1977, in accordance with such modalities as they may
agree upon ;
IN FAVOURPr:e sident Schwebel; Vice-Prr.sident Weeramantry; Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi. Koroma, Vereshchetin,
Parra-Aranguren, Kooijmans, Rezek; Judge ad hoc Skubiszewski;
AGAINST : Judges Herczegh, Fleischhauer ;
C. By thirteen votes to two,
Fin& that, unless the Parties otherwise agree, a joint operational
régime must be established in accordance with the Treaty of 16 September
1977;
IN FAVOUR : President Schwebel ; Vice-Pre.~ident Weeramantry ; Judges
Oda, Bedjaoui, Guillaume, Ranjeva, Shi, Koroma, Vereshchetin,
Parra-Aranguren. Kooijmans, Rezek ; Judge ad hoc Skubiszewski ;
AGAINST : Judges Herczegh, Fleischhauer :
D. By twelve votes to three,
Finds that, unless the Parties otherwise agree, Hungary shall compensate
Slovakia for the damage sustained by Czechoslovakia and by
Slovakia on account of the suspension and abandonment by Hungary
of works for which it was responsible; and Slovakia shall compensate
Hungary for the damage it has sustained on account of the
putting into operation of the "provisional solution" by Czechoslovakia
and its maintenance in service by Slovakia;
IN FAVOURPr:e sident Schwebel; Vice-Puesident Weeramantry; Judges
Bedjaoui. Guillaume, Ranjeva, Herczegh, Shi, Fleischhauer, Parra-
Aranguren, Kooijmans, Rezek; Judge ad hoc Skubiszewski;
AGAINST: Judges Oda. Koroma, Vereshchetin;

E. By thirteen votes to two,
Finds that the settlement of accounts for the construction and
operation of the works must be effected in accordance with the relevant
provisions of the Treaty of 16 September 1977 and related
instruments, taking due account of such measures as will have been
taken by the Parties in application of points 2 B and 2 C of the
present operative paragraph.
IN FAVOURPr:e sident Schwebel; Vice-President Weeramantry; Judges
Oda, Bedjaoui, Guillaume, Ranjeva. Shi, Koroma. Vereshchetin,
Parra-Aranguren, Kooijmans, Rezek; J u d p ad hoc Skubiszewski;
AGAINSJTu:d ges Herczegh, Fleischhauer.
Done in English and in French, the English text being authoritative, at
the Peace Palace, The Hague, this twenty-fifth day of September, one
thousand nine hundred and ninety-seven, in three copies, one of which
will be placed in the archives of the Court and the others transmitted to
the Covernment of the Republic of Hungary and the Government of the
Slovak Republic, respectively.
(Signed) Stephen M. SCHWEBEL,
President.
(Signed) Eduardo VALENCIA-OSPINA,
Registrar.
President SCHWEBEaLn d Judge REZEKa ppend declarations to the
Judgment of the Court.
Vice-President WEERAMANTRaYnd Judges BEDJAOUaI nd KOROMA
append separate opinions to the Judgment of the Court.
Judges ODA, RANJEVAH, ERCZEGHF,L EISCHHAUEVRE,R ESHCHETaInNd
PARRA-ARANGURaEnNd Judge ad hoc SKUBISZEWSaKppI end dissenting
opinions to the Judgment of the Court.
(Initiullcd) S.M.S.
(Initialled) E.V.O.