Custom on a Sliding Scale

Abstract

Every student who has ever taken a traditional international law course has learned Manley Hudson’s four elements for the emergence of a rule of customary international law: ( a ) concordant practice by a number of States with reference to a type of situation falling within the domain of international relations; ( b ) continuation or repetition of the practice over a considerable period of time; ( c ) conception that the practice is required by, or consistent with, prevailing international law; and ( d ) general acquiescence in the practice by other States.