Custom's Method and Process: Lessons from Humanitarian Law

Custom's Future: International Law in a Changing World (Curtis Bradley ed., 2015 Forthcoming)

U of Michigan Public Law Research Paper No. 445

28 Pages Posted: 18 Mar 2015 Last revised: 15 May 2015

See all articles by Monica Hakimi

Monica Hakimi

University of Michigan Law School

Date Written: April 2, 2015


A central question in the literature on customary international law (CIL) goes to method: what is the proper method for “finding” CIL — that is, for determining that particular norms qualify as CIL? The traditional method is to identify a widespread state practice, plus evidence that states believe that the practice reflects the law. That method is widely perceived to be inadequate, so much of the literature focuses on correcting its flaws. The principal goals of this literature are to help resolve whether norms that are claimed to be CIL are really CIL, and thus to reduce the volatility and susceptibility to abuse in CIL.

I argue in this book chapter that the method for finding CIL might be so elusive because the question itself is misconceived. The question of how to find CIL presupposes that finding CIL is an objective exercise and somehow removed from the process for making CIL. This process is notoriously undisciplined and politically charged. Disparate actors make CIL by advancing and responding to one another's legal claims, as they promote their own interests. The methodological question assumes that CIL-finding is distinct — that actors who find CIL do not advance their own agendas but rather assess the evidence objectively, and thus that their decisions help settle CIL by weeding out invalid claims. I use the recent rise of CIL in international humanitarian law to show that these assumptions are flawed. CIL-finding is deeply entangled with CIL-making. The two exercises operate in much the same way and through the same process, so they share similar limitations. My argument here has two practical implications. First, non-state actors can play a much larger role in the formation of CIL than the literature now recognizes. Second, methods for finding CIL are unlikely to discipline global actors or to impose order on CIL, as long as the process for making CIL remains so undisciplined and disordered.

Keywords: international law, customary international law, international humanitarian law, law of armed conflict, international legal theory, international lawmaking

Suggested Citation

Hakimi, Monica, Custom's Method and Process: Lessons from Humanitarian Law (April 2, 2015). Custom's Future: International Law in a Changing World (Curtis Bradley ed., 2015 Forthcoming), U of Michigan Public Law Research Paper No. 445, Available at SSRN:

Monica Hakimi (Contact Author)

University of Michigan Law School ( email )

625 South State Street
Ann Arbor, MI 48109-1215
United States

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