According to this principle (understood in a broad sense), extraordinary circumstances can lead to the termination of a treaty. These circumstances can consist either in a material breach of a given treaty by one of the States Parties (Article 60), in a permanent disappearance of an object indispensable for the execution of the treaty (Article 61) or in a fundamental change of circumstances (Article 62, clausula rebus sic stantibus understood in a narrow sense).
A fundamental change of circumstances can also occur in the case of the outbreak of hostilities between the States Parties (see Article 73). However, this fact cannot be invoked as a ground for terminating a treaty, if it has been concluded with regard to the possible outbreak of an armed conflict as in the case of the Geneva Conventions of 12 August 1949 (so-called Red Cross-conventions) or the Hague Conventions of 1899 and 1907.
A further extraordinary circumstance foreseen by the Vienna Convention is the emergence of "jus cogens" , i.e. of a new peremptory norm of general international law. This circumstance is distinct from those enumerated above by the fact that it is of normative and not factual nature. The rebus sic stantibus clause can be considered as an implicit reservation generally affecting the consent expressed by a State to be bound by a treaty. It seems worthwhile mentionning in this context that Argentina has made a reservation to Article 62 in which it made plain that she would not not accept the idea that 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 be invoked as a ground for terminating or withdrawing from the treaty.
However, according to Article 62 (2)(a) (rebus sic stantibus clause understood in a narrow sense), a fundamental change of circumstances may not be invoked in the case of boundary treaties, the reason being that putting into question international boundaries can lead to a peace theatening situation, because it jeopardizes the principle of territorial integrity (see Article 2 (4) of the Charter of the United Nations) which is quite fundamental in international relations.
Hence, the Vienna Convention on Succession of States in respect of Treaties of 1978 has restated the rule that a succession of States does not affect as such a boundary or any other territorial regime established by a treaty.
