ICJ Opinion about Impossibility of Performace of gabcikovo case

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.

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.