A member state is a state that is a member of an international organization or of a federation or confederation.
Since the World Trade Organization (WTO) and the International Monetary Fund (IMF) include some members that are not sovereign states, neither organization ever speaks of "member states". The WTO has simply "members" (see WTO members), and the IMF refers to its members as "member countries".
Customary international law consists of international legal obligations arising from established or usual international practices, which are less formal customary expectations of behavior often unwritten as opposed to formal written treaties or conventions. Customary law is also referred to as opinio juris (means “opinion of law”), which is a term used in international law to signifiy state practices taken under the belief that such actions are legal obligations. Generally, customary international law applies equally to all states. Along with general principles of law and treaties, custom is considered by the International Court of Justice, jurists, the United Nations, and its member states to be among the primary sources of international law.
Rules that are considered customary law are binding upon all states. Customary international law need not be codified in a treaty. If a treaty, or any portion thereof, becomes customary law, it will bind all states that are not persistent objectors. A treaty or international agreement can bind a state not party to the treaty when: the treaty codifies customary international law; or when the treaty has become customary law or represents an obligation erga omnes. For example, the Vienna Convention on the Law of Treaties is widely described as codifying customary international law concerning treaties.
The North Atlantic Treaty Organization (NATO) is an international military alliance consisting of 32 member states from Europe and North America. It was established at the signing of the North Atlantic Treaty on 4 April 1949. Of the 32 member countries, 30 are in Europe and two are in North America. Between 1994 and 1997, wider forums for regional cooperation between NATO and its neighbours were set up, including the Partnership for Peace, the Mediterranean Dialogue initiative, and the Euro-Atlantic Partnership Council.
All members have militaries, except for Iceland, which does not have a typical army (but it does have a coast guard and a small unit of civilian specialists for NATO operations). Three of NATO's members are nuclear weapons states: France, the United Kingdom, and the United States. NATO has 12 original founding member states. Three more members joined between 1952 and 1955, and a fourth joined in 1982. Since the end of the Cold War, NATO has added 16 more members from 1999 to 2024. Article 5 of the treaty states that if an armed attack occurs against one of the member states, it shall be considered an attack against all members, and other members shall assist the attacked member, with armed forces if necessary. Article 6 of the treaty limits the scope of Article 5 to the islands north of the Tropic of Cancer, the North American and European mainlands, the entirety of Turkey, and French Algeria, the last of which has been moot since July 1962. Thus, an attack on Hawaii, Puerto Rico, French Guiana, the Falkland Islands, Ceuta or Melilla, among other places, would not trigger an Article 5 response.
The European University Institute (EUI) is an international postgraduate and post-doctoral research-intensive university and an intergovernmental organisation with juridical personality, established by its founding member states to contribute to cultural and scientific development in the social sciences, in a European perspective. Its main campus is located in the hills above Florence in Fiesole, Italy.
The EUI is funded by its 24 Contracting States, the European Union (Erasmus+), and its own revenue, drawn from competitive research funding, partnerships with public and private actors, and executive education.
The Community of Portuguese Language Countries consists of nine member states, which list the Portuguese language as an official language, and only East Timor and Equatorial Guinea list a secondary official language (Tetun and Spanish respectively).
In 2005, during the CPLP Council of Ministers meeting in Luanda, the status of associate observer for non-member states was adopted to enhance international cooperation and achieve the Community's objectives, leading to the subsequent admission of three states.