Abstract

The position of the exceptio non adimpleti contractus in public international law as a response to the breach of a treaty is surrounded by uncertainty. This article aims to offer an analytical examination of I) the notion of the exceptio and its relationship to other responses to the breach of a treaty; II) the question of its conditions of application; and III) its character as a rule of international law. It argues that the exceptio is distinct both from responses pursuant to Art 60 VCLT and from countermeasures; however, there is uncertainty with regard to its conditions of application. It can be considered as a general principle of law and, as such, it can fill gaps in the regulation of responses to the breach of a treaty. However, it is not clear whether the exceptio constitutes a rule of customary international law.