Citation. I.C.J., 1977 I.C.J. 7 (1997)
Brief Fact Summary. Hungary (D) asserted that the enforcement of a treaty with Slovakia (P) would not be possible because of changes in circumstances.
Synopsis of Rule of Law. A vital change of circumstances must have been unforeseen and 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 their agreement.
Issue. In 1977, Hungary (D) and Slovakia (P) agreed to build and operate a system of locks along the Danube River made up of a dam, reservoir, hydroelectric power plant and flood control improvements. This project never saw the light of the day and the two countries went through different changes in their political and economic systems beginning in 1989. Hungary (D) was the first to stop and abandon its part of the works and later give notice of termination of the treaty. In 1992 and based on international law, both countries asked the I.C.J. to decide whether Hungary (D) was entitled to suspend and subsequently abandon its part of the work, on the grounds of the doctrine of impossibility of performance.
Held. Yes. A vital change of circumstances must have been unforeseen and 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 their agreement. Where the common political and economic conditions were not so closely related to the goals and purpose of the treaty as to constitute an essential basis of the consent of the parties, there was no fundamental change of circumstances.it is only in exceptional cases that the plea of fundamental change of circumstance may be applied
Discussion. The Court relied on the Vienna Convention. The Convention may be seen as a codification of existing customary law on the subject of termination of a treaty on the basis of change in circumstances. New developments in environmental law were not completely unforeseen.