Customary Law - Public International Law Research - A Brief Guide - LibGuides at University of San Francisco School of Law

Advice on Researching Customary Law

Researching customary law is as complex as it is essential. Some useful (but by no means all) sources include: digests of state practice (for those nations that keep them); domestic/municipal law; and international law yearbooks. Actions by international governmental organizations (such as the U.N.) may also serve as evidence of customary law. For these actions, see the United Nations/IGOs section of this guide.

These are some good online and print guides on researching customary law. Where good digital sources for customary law research are available, the online guides will take you to them.

Researching Customary International Law, State Practice and the Pronouncements of States regarding International Law
By Silke Sahl of Columbia and Catherine Deane of Shearman & Sterling. Part of the GlobaLex collection of foreign and international research guides. (Updated in 2018.)
Other Sources of International Law [primarily Customary International Law]
A very thorough guide from the Boston University's Pappas Law Library, "covering the sources of customary international law."
Customary International Law: Research Guides & Background Information
A section of the helpful International Legal Research Tutorial. (A collaboration between Duke University School of Law and University of California, Berkeley, School of Law.)
Researching Public International Law: Custom and State Practice
By Kent McKeever of Columbia University's Arthur W. Diamond Law Library. (Published in 2006.)
Research Guide to Customs, General Principles, & the Teachings of Highly Qualified Publicists
A 14-page PDF guide by Lee Peoples of the Oklahoma City University Law Library. (Published in 2005.)

Sources of State Practice in International Law, 2d ed. by Ralph F. Gaebler & Alison A. Shea, eds.
Call Number: KZ 64 .S67 2014 Law Reference
ISBN: 9004178864
Publication Date: 2014

United States Practice - Digests

Digest of United States Practice in International Law, 1989-
A "historical record of the views and practice of the Government of the United States in public and private international law." Supplemented, in many cases, with the full-text documents referenced in the Digest. Also in print: KZ 21 .R68 Law Stacks.
Cumulative Digest of United States Practice in International Law, 1981-1988
From the U.S. Department of State. (Provided here by HeinOnline — for current USF students, faculty, and staff.) Also in print: KZ 21 .R68 Law Stacks. [On-campus link for Cum. Digest of United States Practice in Int'l Law, 1981-1988.]
Digest of United States Practice in International Law, 1973-1980
From the U.S. Department of State. (Provided here by HeinOnline — for current USF students, faculty, and staff.) [On-campus link for Digest of United States Practice in Int'l Law, 1973-1980.]
Digest of International Law (Whiteman), 1940-1960
From the U.S. Department of State & compiled by Marjorie M. Whiteman. (Provided here by HeinOnline — for current USF students, faculty, and staff.) In print: JX 237 .W5 Law Compact Storage. (Dates of coverage vary by topic.) [On-campus link for Digest of International Law (Whiteman), 1940-1960.]
A Digest of International Law, 1776-1906
Compiled by John Bassett Moore. A revision of Wharton's Digest of the International Law of the United States. (Provided here by HeinOnline — for current USF students, faculty, and staff.) Also in print: JX 237 .M66 1906 Law Compact Storage.[On-campus link for A Digest of International Law, 1776-1906.]
A Digest of the International Law of the United States
Compiled by Francis Wharton and published in 1886. (Provided here by HeinOnline — for current USF students, faculty, and staff.) Also in print: JX 237 .W5 1886 Law Compact Storage. [On-campus link for Digest of the International Law of the United States (Wharton).]
Digest of Published Opinions of the Attorneys-General and of the Leading Decisions of the Federal Courts, with Reference to International Law, Treaties, and Kindred Subjects
Compiled by John L. Cadwalader. Published in 1877. (Provided here by HeinOnline — for current USF students, faculty, and staff.) [On-campus link for Digest of Published Opinions of the Attorneys-General and of the Leading Decisions of the Federal Courts.]
History and Digest of the International Arbitrations to Which the United States Has Been a Party
Compiled by John Bassett Moore. Published in 1898. (Provided here by HeinOnline — for current USF students, faculty, and staff.) [On-campus link for History and Digest of Int'l Arbitrations (U.S. as Party).]

United States Practice - Other Sources

These are just a few of the many other useful sources for researching United States state practice in international law. For more options, see "Advice on Researching Customary Law," above.

Foreign Relations of the United States (FRUS) - HeinOnline This link opens in a new window
This HeinOnline version covers 1861 to the present. The U.S. Dep't of State has some 20th century portions of the Foreign Relations of the U.S. The Univ. of Wisconsin has a version of Foreign Relations of the United States covering 1861 - 1960.

Contemporary Practice of the United States Relating to International Law - American Journal of International Law (HeinOnline)
Each issue of the American Journal of International Law includes a section on the "Contemporary Practice of the United States Relating to International Law." The journal is also in print at: K1 .M456 Law Stacks.
[On-campus link for Contemporary Practice of the United States Relating to Int'l Law - Am. J. Int'l Law.]
United States Practice in International Law (2002- )
By Sean D. Murphy. In print: KF 4581 .M87 2002 Law Stacks. (USF currently has the first of two volumes.)

State Practice of Foreign Nations

Here are some good places to begin your search for state practice of non-U.S. nations. For more options, see "Advice on Researching Customary Law," above.

International Yearbooks - HeinOnline
Yearbooks on international law often reproduce key documents relating to state practice. This HeinOnline collection includes 16 national yearbooks and several topical yearbooks. (For current USF students, faculty, and staff.) [In print the Zief Library has the Asian, British, Canadian, and South African yearbooks, and early volumes of the Australian and Italian yearbooks.] [On-campus link for International Yearbooks.]
Commentaries on the Draft Articles on State Responsibility [PDF]
These Commentaries (from the International Law Commission) can be a rich source of citations for building arguments about state practice and customary law.

Domestic/Municipal Law of Foreign Nations

Domestic laws (including constitutions) can provide evidence of customary law, as well as of "general principles." Here are a few places to start.

Researching Foreign Legal Systems - Basic Resources
An introductory guide to researching the laws of non-United-States nations.
Guide to Law Online: Nations of the World - Library of Congress
Useful for finding constitutions and selected other legal sources.

Oxford Constitutional Law - Constitutions of the World This link opens in a new window
"Fully-translated English-language versions of all the world's constitutions (both national and sub-national), accompanied by individual jurisdictional commentaries, and supplementary materials, including foundation documents, historical versions of constitutions, and amendment Acts/Laws." Includes the U.S. Federal constitution, plus access to Oxford's "U.S. Constitutional Law" module (for U.S. state constitutions). Oxford Constitutional Law - Constitutions of the World link for USF on-campus access.
World Constitutions Illustrated - HeinOnline This link opens in a new window
Current and historical constitutions; books; articles; selected web sites. (For current USF students, faculty, and staff.)

Customary Humanitarian Law

International Humanitarian Law - Treaties & Documents - ICRC
"The database contains a hundred or so treaties and instruments of international humanitarian law from 1856 to the present." Organized by topic and date.
Customary International Humanitarian Law Database - ICRC
For international humanitarian law issues, this database, from the International Committee of the Red Cross, is a good first stop. It sets forth the 161 rules of international humanitarian law humanitarian law, and the practice underlying those rules.
National Implementation - Humanitarian Law - ICRC Database
"Documentation and commentaries concerning the implementation of international humanitarian law at the national level." Includes laws, regulations, and cases. Can be searched by nation or key word.