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Pritzker Legal Research Center

International Legal Research Guide

An overview of international law and where to begin research


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." 

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.