General Principles and the Interpretation of CIL

The interpretation of unwritten norms is fraught with difficulty, as the boundaries between the existence of a norm and the determination of its content can become blurred. Interpreters may return to the evidence of the norm’s existence in order to determine its content or it may be that interpretation itself is part of the constitutive process of unwritten norms. This confusion is exacerbated by a lack of established methods and procedures for the interpretation of unwritten international law, which includes not only custom but also general principles of law. While it is commonplace to speak of custom and general principles under the umbrella of ‘general international law’, it is unclear whether questions of interpretation are to be approached in the same manner for both categories of norms or whether custom and general principles may assist in the interpretation of one another. The central objective of this chapter is to examine the interactions between these two categories of norms in the context of interpretation. More specifically, it considers whether general principles of law may play a role in the interpretation of customary rules.