States regularly proclaim the sanctity of treaty obligations and few principles are as firmly established as pacta sunt servanda.1 Yet, treaty breaches are by no means exceptional: adapting one of international law’s most celebrated statements, one might even say that ‘almost all nations, almost all the time, consider their rights under a given treaty to be violated’.2 By way of a snapshot, at the time of writing, six of nine active contentious cases pending before the International Court of Justice (ICJ) involve claims, by one State, that a certain treaty has...