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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