Finding Customary International Law

56 Pages Posted: 18 Sep 2015 Last revised: 8 Aug 2016

See all articles by Ryan Scoville

Ryan Scoville

Marquette University - Law School

Date Written: October 12, 2015


Established doctrine holds that customary international law (CIL) arises from general and consistent state practice that is backed by a sense of legal obligation. Contemporary litigation requires federal courts to apply this doctrine to identify the contours of CIL in a diverse collection of cases ranging from civil actions under the Alien Tort Statute to criminal prosecutions under the Maritime Drug Law Enforcement Act. This Article provides an in-depth look at how federal judges carry out the task. Conducting a citation analysis of opinions published since the U.S. Supreme Court’s 2004 decision in Sosa v. Alvarez-Machain, the Article identifies the form, quality, and geographical origins of the authorities that tend to serve as evidence of custom; explores the implications of recent citation patterns; and offers ideas to help courts grapple more effectively with the challenge of finding custom.

Keywords: Customary International law, Federal Courts, Sosa, Alien Tort Statute, Citation Analysis

Suggested Citation

Scoville, Ryan M., Finding Customary International Law (October 12, 2015). Iowa Law Review, Vol. 101, 2016; Marquette Law School Legal Studies Paper No. 16-08. Available at SSRN:

Ryan M. Scoville (Contact Author)

Marquette University - Law School ( email )

Eckstein Hall
P.O. Box 1881
Milwaukee, WI 53201
United States
720-993-0197 (Phone)

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