The Formation of Customary International Law and Its Methodological Challenges

Abstract

Developing a methodological underpinning for customary international law has been a constant challenge. Indeed, customary law has become an inspiring source for innovative legal theories. Lacking a coherent theoretical basis, critics have suggested that customary international law has an “identity crisis”, or is “situated in a theoretical minefield.” Indeed, there appears to be no common consensus, on either a catalogue of specific rules that have attained the status of customary law, or on the doctrinal and methodological approaches required to establish and determine customary international law as a source of law. When discussing customary international law as a source of international law three levels have to be distinguished: (1) the nature of customary international law, (2) the constitutive elements necessary for the formation of customary international law and (3) the evidence for the identification of customary international law.