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Customary International Law: An Instrument Choice Perspective, Laurence R. Helfer, Ingrid B. Wuerth

Michigan Journal of International Law

This Article proceeds as follows. Part II begins by considering custom’s design features, which the authors distinguish from the canonical elements of custom (state practice and opinio juris) and the individual doctrines associated with CIL. Specifically, they contend that, as an ideal-type, custom is non-negotiated, unwritten, and universal, three characteristics that distinguish CIL from both treaties and soft law, which are almost always negotiated, written, and rarely universal either in formation or application. These design features help to explain some of custom’s peculiar doctrinal characteristics, and they cut across the doctrinal divide which is said to distinguish “traditional” and …