Pritzker Legal Research Center: International Legal Research Guide: Customary International Law

Overview

A rule of customary international law is demonstrated by showing evidence of two elements: (1) state practice (objective element); and (2) opinio juris (subjective element).

Evidence of State Practice in the United States

Digests provide insight into the "view and practice of the Government of the United States in the arena of public and private international law."

U.S. State Department: Digest of United States Practice in International Law
Contains annual volumes from 1989-1990, 1991-1999, and 2000-2016 (note that there was a hiatus in publication from 1989-1999).
U.S. State Department: Foreign Relations of the United States
This series is the official documentary historical record of major U.S. foreign policy decisions and significant diplomatic activity.
HeinOnline: U.S. Law Digests
Contains Cumulative Digest of United States Practice in International Law, 1981-1988, Digest of United States Practice in International Law, and other digests.

Evidence of State Practice in Other Jurisdictions

Check Sources of State Practice in International Law to locate compiled state papers. Governmental websites, particularly those of foreign ministries, can be useful sources of information on the current international practice of the given country. Additionally, international law yearbooks often contain information on current state practice.

Sources of State Practice in International Law by Ralph Gaebler; Alison A. Shea
Call Number: Non-Circulating: I,REF KZ64 .S67 2014
Publication Date: 2014
"Sources of State Practice in International Law is a descriptive bibliography of both electronic and printed sources of information containing the text of treaties and the record of diplomatic activity of important jurisdictions around the world. As such, it includes an up-to-date description of national treaty portals and other valuable Internet-based sources. At the same time, it also includes descriptions of printed sources providing access to treaties and official diplomatic documentation difficult to locate in standard compilations. In addition, this work includes a narrative section for each jurisdiction summarizing issues related to treaty succession and treaty implementation in municipal law. Sources of State Practice in International Law is an indispensable reference for researchers in both international law and international relations." - Publisher

HeinOnline: International Yearbooks and Periodicals