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Public International Law: Basic Concepts

Guidance for researching subjects related to public international law.

For a basic overview of treaties, see Treaty Section of the Office of Legal Affairs, Treaty Handbook, U.N. Sales No. E.12.V.1 (2012),

Important Concepts

  • Various terms for treaties: convention, protocol, covenant charter, statute, act, declaration
  • IGOs: intergovernmental organizations. Associations of states established pursuant to a treaty that has a legal personality separate and distinct from its member states and has the ability to enter into binding agreements with other IGOs or states. Example: the United Nations. 
  • NGOs: nongovernmental organizations. "Any scientific, professional, business, or public-interest organization that is neither affiliated with nor under the direction of a government; an international organization that is not the creation of an agreement among countries, but rather is composed of private individuals or organizations." Black's Law Dictionary (10th ed. 2014).
  • Bilateral treaties: agreement between two parties. 
  • Multilateral treaties: agreement between three or more parties. 
  • Treaty v. executive agreement in U.S. law: Treaties to which the U.S. is a party are part of federal legislation and must go through the Senate to become ratified, and to become part of "the supreme law of the land." Treaties are made "by and with the advice and consent of the Senate" (U.S. CONST. art. II, § 2, cl. 2). There may also be Sole Executive agreements and Congressional-Executive agreements. For a full overview view, see Frederic L. Kirgis, International Agreements and U.S. Law, Am. Soc'y of Int'l L. (May 27, 1997),; 11 U.S. Dep't of State, Foreign Affairs Manual §§ 723-24,
  • Unperfected treaties: a treaty that has not been given binding and full effect. For a U.S. treaty, this could mean that is not ratified by the end of a Congressional session. These agreements may still be given judicial effect. W. Michael Reisman, Unratified Treaties and Other Unperfected Acts in International Law: Constitutional Functions, 35 Vand. J. Transnat'l L. 729 (2002).
  • Limiting application of a treaty: reservations, declarations, and understandings. If a country does not accept every provision of the treaty, it may have the option to limit complete application of the treaty. For a discussion of these terms and how they interact with one another, see Restatement (Third) of the Foreign Relations Law of the United States § 313 (Am. Law Inst. 1987), Westlaw (database updated June 2015).