Although it is clear that a fundamental change of circumstances might justify terminating or modifying a treaty, unilateral denunciation of a treaty is prohibited; i.e. a party does not have the right to denounce a treaty singlehandedly.
If the parties to a treaty had contemplated for the occurrence of the changed circumstance, the doctrine will not apply and instead, the provision will take effect. Clausula rebus sic stantibus only relates to changed circumstances that were never contemplated by the parties. This principle is clarified in the Fisheries Jurisdiction Case; United Kingdom v. Iceland 
Otto von Bismarck said that all treaties should contain this phrase.