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Foreign, Comparative & International Law

Key Concepts

"Public international law governs the relationships between national governments and intergovernmental organizations. It regulates governments and intergovernmental organizations across national boundaries." Marci Hoffman and Katherine TopolosInternational Legal Research Tutoria: Public International Lawl (last visited Jan. 23, 2013).


International law. (18c) The legal system governing the relationships between nations; more modernly, the law of international relations, embracing not only nations but also such participants as international organizations and individuals (such as those who invoke their human rights or commit war crimes). — Also termed public international law; law of nations; law of nature and nations; jus gentium; jus gentium publicum; jus inter gentes; foreign-relations law; interstate law; law between states (the word state, in the latter two phrases, being equivalent to nation or country). Cf. transnational law
“[I]nternational law or the law of nations must be defined as law applicable to states in their mutual relations and to individuals in their relations with states. International law may also, under this hypothesis, be applicable to certain interrelationships of individuals themselves, where such interrelationships involve matters of international concern.” Philip C. Jessup, A Modern Law of Nations 17 (1949).
INTERNATIONAL LAW, Black's Law Dictionary (9th ed. 2009), international law

Sources of International Law - Video

Sources of Law
Video link
  (40 minutes)

Source:  United Nations Audio Visual Library, The Sources of International Law

Judge Christopher Greenwood, International Court of Justice

Codification Division, Office of Legal Affairs
Copyright © United Nations, 2017. All Rights Reserved.

Terms and Conditions of Use.

Sources as Recognized by the International Court of Justice

a. International Conventions, whether general or particular, establishing rules expressly recognized by the contesting states;

b. International Custom, as evidence of a general practice accepted as law;

c. the General Principles of Law recognized by civilized nations;

d. subject to the provisions of Article 59, Judicial Decisions and the Teachings of the Most Highly Qualified Publicists of the various nations, as subsidiary means for the determination of rules of law.


Article 38, ¶ 1. of the Statute of the International Court of Justices

The U.S. Perspective

The U.S. Perspective

From the Restatement (Third) of Foreign Relations Law § 102 (1987)

 (1) A rule of international law is one that has been accepted as such by the international community of states

(a) in the form of customary law;
(b) by international agreement; or
(c) by derivation from general principles common to the major legal systems of the world.
(2) Customary international law results from a general and consistent practice of states followed by them from a sense of legal obligation.
(3) International agreements create law for the states parties thereto and may lead to the creation of customary international law when such agreements are intended for adherence by states generally and are in fact widely accepted.
(4) General principles common to the major legal systems, even if not incorporated or reflected in customary law or international agreement, may be invoked as supplementary rules of international law where appropriate.
The 4th edition of the Restatement is available. It does not alter  § 102.
Other Sources

Rüdiger WolfrumSources of International Law, Max Planck Encyclopedia of Public International Law (last updated May 2011)

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