Traditional and Modern Approaches to Customary International Law: A Reconciliation

Abstract

The demise of custom as a source of international law has been widely forecasted. This is because both the nature and the relative importance of custom’s constituent elements are contentious. At the same time, custom has become an increasingly significant source of law in important areas such as human rights obligations. Codification conventions, academic commentary, and the case law of the International Court of Justice (the Court) have also contributed to a contemporary resurrection of custom. These developments have resulted in two apparently opposing approaches, which I term “traditional custom” and “modern custom.” The renaissance of custom requires the articulation of a coherent theory that can accommodate its classic foundations and contemporary developments. This article seeks to provide an enriched theoretical account of custom that incorporates both the traditional and the modern approaches rather than advocating one approach over the other.