The Relationship Between Customary International Law and General Principles of Law

Abstract

IMPORTANT CONCEPTS What is the proper distinction between customary international law and general principles of law? To resolve this issue, it is first helpful to define certain key terms. According to the proposed definition of opinio juris , customary international law includes “principles” as well as “rules.” A “rule” typically lays down a fairly specific binding obligation, although it can also define a reasonably specific persuasive obligation. A “principle” is less specific and normally establishes a persuasive obligation to give some value or action great weight in decision making. A “general principle” is a principle that is broad in scope and applies across a wide range of subject areas. Both principles and rules are types of “norms.” A number of scholars have agreed with some of these basic propositions. For example, the International Law Association has stated that “principles operate at a higher level of generality than rules.” Wolfke has noted that general principles “are certainly the most abstract norms, and hence the will of states is least objectified in them.” At first blush, it would appear that the definition of customary international law I propose would blur the boundaries of the two concepts of customary international law and general principles of law. If the requirement of state practice, in other words “custom,” is relaxed and practice is treated merely as one source of evidence of opinio juris , then what remains to distinguish customary law from general principles of law?