International Law’s Erie Moment

61 Pages Posted: 5 Sep 2012 Last revised: 29 Oct 2015

See all articles by Harlan Grant Cohen

Harlan Grant Cohen

Fordham University School of Law; University of Georgia School of Law; University of Georgia - Dean Rusk International Law Center

Date Written: September 5, 2012


Who fills international law’s gaps? Whether over the meaning of bilateral investment treaties, the standards regarding detainee transfer, or the rules of non-international armed conflict, courts and states are increasingly in conflict over the authority to say what the law is. With international law’s increased judicialization, two competing visions of international law have emerged: One, a gap-filled international law, in which law is developed slowly through custom, argument, and negotiation, and a second, gap-less, in which disputes are resolved through a form of common law adjudication.

Drawing on growing literature on the law outside of courts, particularly out-of-court settlements, the social norms of specialized business communities, and constitutional separation-of-powers, along with traditional customary international law, this paper demonstrates that the conflict between these two visions is much deeper than previously assumed. What emerges from these literatures are two radically different models of lawmaking, “negotiated law” and “adjudicated law,” that look different, act differently, rely on different sources of authority and legitimacy, and are to some extent in conflict with one another. Contrary to conventional wisdom, gap-filling by states and gap-filling by courts are not interchangeable.

The unrecognized differences between these two competing models of modern international law lie at the heart of longstanding doctrinal tensions over the nature/sources of customary international law and provide unseen inspiration for the brewing conflicts between courts and states for interpretative supremacy. International law has essentially reached its Erie moment. Only by recognizing the true nature of the conflict, only by recognizing the very different sources of judicial and state authority, only by forcing courts and states to justify their claims to interpretive authority, can we begin to resolve the tensions between these two models and discern the proper roles of courts and states on a modern international law.

Keywords: international law, international tribunals, interpretation, negotiated law, adjudicated law, international adjudication, precedent, treaties, non-treaty international law, custom, general principles of international law, international common law

JEL Classification: K33

Suggested Citation

Cohen, Harlan Grant, International Law’s Erie Moment (September 5, 2012). Michigan Journal of International Law, Vol. 34, 2013, UGA Legal Studies Research Paper No. 2012-11, Available at SSRN:

Harlan Grant Cohen (Contact Author)

Fordham University School of Law ( email )

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University of Georgia School of Law ( email )

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706-542-5166 (Phone)

University of Georgia - Dean Rusk International Law Center ( email )

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Athens, GA 30602-6018
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