Clausula rebus sic stantibus is the legal doctrine allowing for a contract or a treaty to become inapplicable because of a fundamental change of circumstances.
In public international law the doctrine essentially serves an "escape clause" to the general rule of pacta sunt servanda (promises must be kept).
[1]: 28 Because the doctrine is a risk to the security of treaties, as its scope is relatively unconfined, the conditions in which it may be invoked must be carefully noted.
[1]: 31–32 The principle of clausula rebus sic stantibus exists in all legal systems which descend from Roman law.
A key figure in the formulation of clausula rebus sic stantibus was the Italian jurist Scipione Gentili (1563–1616), who is generally credited for coining the maxim omnis conventio intelligitur rebus sic stantibus ('every convention is understood with circumstances as they stand').