International Law Research Guide: State Practice

Definitions of State Practice

A requirement for the existence of customary international law , together with opinio juris , is state practice or the actual actions or omissions of states . Article 38, paragraph 1, subparagraph b, of the Statute of the International Court of Justice states that the practice relevant to establishing customary international law is that which is general and accepted as law. The last part of this paragraph refers to the element of opinio juris , but it is the word “general” that is of importance. It indicates that general, or widespread, practice— not isolated practice— is important. Determining what constitutes state practice usually requires examining historical records that indicate how states act. The more reliable the record the better evidence it is of state practice. - Doebbler, Curtis F. J.

State Practice Research

A few sources that compile State Practice:

Records of a State's Foreign Relations & Diplomatic Practices

Official Treaty Publications

Diplomatic Documents

U.S. State Practice

Legislation Concerning a Country's International Obligations

Practice of IGOs

International Digests

Repertories (Digests to the Practice of IGOs)

Yearbooks of States, Regions, Organizations and Topics

Surveys of state practice organized by treaty and international activities. (Legislation, case law and diplomatic practice). 

IGO Yearbooks

A few examples are provided below.

Topical Yearbooks

A few examples are provided below.