The doctrine of fundamental change of circumstances, (rebus sic stantibus) is a principle of customary international law allowing a part to an agreement to withdraw or terminate it where there has been a fundamental change in circumstances. The main justification for this principle is that treaties often remain in force for many years, during which time fundamental changes may occur in the political or international environment which may require a departure from the provisions set out in the treaty. However, this principle has also been criticized for disrupting the binding force of obligations taken by states, particularly when bearing in mind that there is no compulsory jurisdiction forcing states who terminate a treaty on this ground, to have the legitimacy of their decision scrutinised before an international tribunal.
Nevertheless, this principle has been codified in Article 62 of the VCLT, although its scope has been severely restricted. Article 62 (1) is drafted it negative terms, stating that a fundamental change of circumstances which has occurred since 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
(b) the effect of the change is radically to transform the extent of obligations still to be performed under the treaty.
English: President Reagan and General Secretary Go...
Russia
English: President Jimmy Carter and Soviet General...This is further restricted by Article 62 (2) which states that fundamental change of circumstances may not be invoked as a ground for terminating or withdrawing from a treaty if the treaty establishes a boundary or 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...