Angst of the Exceptio Inadimplenti Non Est Adimplendum in International Law

The legal character of the exceptio inadimplenti non est adimplendum or exceptio inadimpleti contractus is one of those institutions in international law the legal character of which remains somewhat shrouded in mystery. In broad brushstrokes, the exceptio implies that ‘a condition for one party’s compliance with a synallagmatic obligation is the continued compliance of the other party with that obligation’. There are a myriad of unresolved issues concerning the exceptio which are both of a theoretical and a practical nature. As will be explained, there are different forms of the exceptio—a fact which is frequently overlooked. The relationship of the exceptio with the rules on countermeasures and material breach of a treaty are very unclear and have yet to be examined and analysed in depth. From a more theoretical point of view, it is interesting to explore whether the exceptio belongs to general principles of law as enshrined in Article 38(1)(c) of the Statute of the International Court of Justice (ICJ) or, rather, whether it should be approached as a principle relating to cognate obligations which exist more frequently in treaty obligations.