Between Pragmatism and Disenchantment: The Theory of Customary International Law after the ILC Project

Abstract

--- REVISED VERSION --- There is a fundamental, eternal and unresolvable conundrum at the heart of customary international law: we do not know on what we should base our arguments. We seem to periodically rediscover arguments which generations upon generations before us have made and the debates on the theory of customary international law continue unabated, because there is a continuing and strong belief that we need it in order to keep international law working. But the question is whether that is (legal) reason enough to consciously or subconsciously change the mechanics of customary law to suit these perceived needs. The ILC concluded its project on customary international law in 2018. It is suffused with the spirit of pragmatism, but it could not avoid taking a stance on the theoretical aspects of this source. On the other side of the equation we find foundational critiques of customary international law, with Jean d’Aspremont as prominent voice. Custom is downgraded to a set of doctrines within the canon of stories international lawyers tell themselves. Both methods have virtues; both have very dangerous vices; both contain the seeds for their own destruction. One aim of this contribution will therefore be an effort to show the relative merits and demerits of these two techniques from a theoretical point of view. I have thus been prompted me to rethink the argument made in my 2004 EJIL article and to reconceptualise my portrayal of the foundation of this source. My work usually stops at the recognition that we cannot find the law which tells us what the rules on customary international law-making are. In this chapter, I will attempt to go a step further. Section 2 will summarise the two approaches. In Section 3, I will use the problem of verbal practice to show the strength and weaknesses of both approaches. Section 4 will focus on the high-level problem: finding what the law says about the sources of international law. I will discuss a new method for conceptualising this elusive level: the Approximatively Plausible Empowerment Norm (AppPEN).