4 Codification and Progressive Development of International Law

In this chapter we turn to a distinctive element of the international law-making process: codification and progressive development. The unwritten character of customary international law rarely makes its identification easy. The evidence of state practice and opinio juris may be scattered, difficult to access, incomplete or contradictory. The claims of states and other relevant actors often differ, as do their views on what constitutes custom. Nor are general principles of law always easy to identify or to define with precision. Judicial decisions and advisory...