Customary International Law

INTRODUCTION

This chapter turns to some of the conceptual enigmas of customary international law identified in Part One. It sketches a normative theory of the authority of customary international law that takes into account the fundamental ethical principles articulated in Chapter 5 and the insights into the concept of authoritative norms explored in Chapter 4. As part of this normative theory I suggest a revised definition of customary international law. Taken together, this theory and that definition will provide the keys to solve many of these conceptual puzzles.

A REVISED DEFINITION OF CUSTOMARY INTERNATIONAL LAW

A new normative theory should be guided by three main principles. First, traditional rules for identifying customary international law should be accorded significant respect. The reason is that these traditional rules are supported by a number of fundamental ethical principles, including states' membership in a global community of states. Second, however, fundamental ethical principles in international law ought to be used as a guide in interpreting and applying the traditional rules of customary law formation and in identifying the content of customary law. Third, these fundamental ethical principles suggest that, from a long-term perspective, it would be ideal for states to help customary law evolve so that it better reflects and implements these ethical principles. But this is a normative ideal regarding future lawmaking; it does not require, as we will see, that fundamental ethical principles themselves be regarded as norms of customary law.