ABSTRACT
Most students of public international law are of the opinion that coming to terms with the nature of international custom goes to the root of understanding international law itself. Francois Geny seeks to understand custom as an original and autonomous source of positive law. According to Geny, custom is a specific form of law and is therefore radically distinct from mere usage, however ancient and universal it may be. It is therefore essential that the interpreter be able to distinguish between usage and custom. Geny’s discussion of the opinio juris has established only the tautological proposition that a practice is legal insofar as it is considered to be legally binding by those who regard it as authoritative. The success of Geny’s theoretical endeavour must be evaluated in the light of the limited theoretical import of his analysis of the custom.
