An interdisciplinary approach to the study of customary international law may offer many ideas and insights both to international lawyers and to international relations scholars. It may, for example, enable us better to understand the origins of the process of customary international law – and thus of obligation within the international legal system – by seeing that process as but one of many similar customary processes which have existed, and continue to exist, in many different societies, at various levels of social, political and legal development.

More specifically, an interdisciplinary approach to customary international law may change the way we think about ‘system consent’, that is, the idea that States have consented to the entire process of customary international law rather than to each individual rule by which they are bound. The members of the various societies within which customary processes operate clearly have differing degrees of awareness as to their own participatory role in the development, maintenance and change of customary rules. In some societies such ‘law-makers’ may only become aware that a customary law process is operating once other law-makers begin to rely on some of the resulting rules in contentious situations. It is therefore possible that customary processes do not even need to be based on the consent of the law-maker to a pre-existing set of ‘secondary’ or ‘constitutional’ rules.