Cohen: The Plural Sources of Customary International Law

Harlan Grant Cohen (Univ. of Georgia - Law) has posted The Plural Sources of Customary International Law (in Interpretation of CIL: Methods, Interpretative Choices and the Role of Coherence, Panos Merkouris, Andreas Follesdal, Geir Ulfstein, Pauline Westerman, Marina Fortuna, & Kostiantyn Gorobets eds., forthcoming). Here's the abstract:

When faced with the inevitable task of interpreting customary international law, what should a court do and what should it consider? Courts and scholars struggle to find an answer in doctrine, as contentious debates demonstrate. But what if the answer is not in doctrine, but in theory? What if fights over interpreting custom really reveal deep disagreement about the nature, source, and authority of custom? This chapter argues that interpreting custom requires a theory (or perhaps theories) of custom. It requires looking behind international law’s doctrine of sources and asking why we consider custom a source of law at all. But exploring the stories we tell to answer that question, this chapter identifies at least three different, competing, perhaps even contradictory concepts of customary international law in common use. Referred to here as Negotiated Law, Legislated Law, and Adjudicated Law, each draws on different sources of legitimacy, operates according to different logics, dictates different methods of interpretation, and favors different methods for resolving disputes. The difficulty for court interpreting custom is thus first figuring out which 'custom' they are interpreting. Only after answering that question, can they figure out what method to apply and what justifications to invoke.