A Nuclear-Weapon-Free Zone (NWFZ) is a delimited geographic space in which a treaty or convention prohibits these weapons of mass destruction.

United Nations General Assembly resolution 3472 B (1975) defines the principal legally binding obligations of the nuclear-weapon States towards Nuclear-Weapon-Free Zones and towards the States included therein:

1. To respect in all its parts the statute of total absence of nuclear weapons defined in the treaty of convention which serves as the constitutive instrument of the zone;
2. To refrain from contributing in any way to the performance in the territories forming part of the zone of acts which involve a violation of the aforesaid treaty or convention;
3. To refrain from using or threatening to use nuclear weapons against the States included in the zone.

There are five NWFZs currently in force on our planet: Latin American and the Caribbean (Treaty of Tlatelolco, opened for signature in 1967); South Pacific (Treaty of Rarotonga, 1985); Southeast Asia (Treaty of Bangkok, 1995); Africa (Treaty of Pelindaba, 1996); Central Asia (Treaty of Central Asia, 2006); and the territory of Mongolia, which in 2000 gained international recognition as a State free of nuclear weapons through Resolution 55/335 S of the United Nations General Assembly.

The Treaty for the Prohibition of Nuclear Weapons in Latin American and the Caribbean – known as the Treaty of Tlatelolco – is the legal instrument signed and ratified by all 33 countries of Latin America and the Caribbean. It prohibits: the testing, use, manufacture, production or acquisition by any means whatsoever of any nuclear weapons, directly or indirectly, within said region.

It commits its contracting parties to use exclusively for peaceful purposes the nuclear material and facilities which are under their jurisdiction (Article 1). By this means, the Treaty of Tlatelolco established the NWFZ of Latin America and the Caribbean.

The Treaty of Tlatelolco delineates its Zone of Application (Article 4); it creates and sets the structure, powers, and activities for the Agency (OPANAL) which oversees compliance with the obligations of the Contracting Parties (Articles 6, 7, 8, 9, 10, 11, 19, 22, and 23); it establishes a Control System, under OPANAL, and the International Atomic Energy Agency (Articles 12, 13, 14, 15, and 16).

The Treaty contains two Additional Protocols, Protocols I and II, aimed in the first instance, towards ensuring the militarily denuclearized status of those territories in the Zone of Application that are, de jure or de facto, under the control of extraterritorial  States and, in the second instance, it includes a legally binding obligation of nuclear weapon States not to deploy nuclear weapons within the Treaty´s Zone of Application, and not to use or threaten to use nuclear weapons against any of the Contracting Parties.

The Latin American and Caribbean States, through the Treaty of Tlatelolco, seek to: ”contribute towards ending the armaments race, especially in the field of nuclear weapons, and towards strengthening a world at peace, based on the sovereign equality of States, mutual respect and good neighborliness” (paragraph 2 of the preamble of the Treaty of Tlatelolco).

All 33 countries of Latin America and the Caribbean are Contracting Parties of the Treaty of Tlatelolco and, consequently, States Members of OPANAL: Antigua and Barbuda, Argentina, Bahamas, Barbados, Belize, Bolivia, Brazil, Chile, Colombia, Costa Rica, Cuba, Dominica, Dominican Republic,  Ecuador, El Salvador, Grenada, Guatemala, Guyana, Haiti, Honduras, Jamaica, Mexico, Nicaragua, Panama, Paraguay, Peru, Saint Kitts and the Nevis, Saint Lucia, Saint Vincent and the Grenadines, Suriname, Trinidad and Tobago, Uruguay, and Venezuela.

OPANAL is made up of three main bodies: The General Conference; the Council; and the Secretariat, in charge of a Secretary-General.

The General Conference is the principal body of the Agency, being made up of all Member States. It holds regular meetings where decisions regarding the functions and the international Agenda of OPANAL are made.

The Council is made up of five Member States of the Agency – currently Argentina, Belize, Honduras, Nicaragua and Uruguay. The members of the Council are elected by the General Conference and meet regularly to oversee, through the Secretary-General, the proper functioning of the Control System established by the Treaty of Tlatelolco.

The Secretariat is composed of a Secretary-General and the staff required by the Secretary-General. The Secretary-General serves in his position for a period of four years, and is eligible for reelection only for a second period.In accordance with the decisions of the General Conference and the Council, the Secretary-General is responsible for ensuring the proper functioning of the Control System established by the Treaty of Tlatelolco.

In accordance with Article 7 of the Treaty of Tlatelolco, the OPANAL headquarters is located in Mexico City. The address is Calle Milton 61, Colonia Anzures, Alcadía Miguel Hidalgo, C.P. 11590, Mexico City.

The Control System referred to in Article 12 of the Treaty of Tlatelolco is carried out by two international organizations: OPANAL and the International Atomic Energy Agency (IAEA). Article 13 of the Treaty commits the Contracting Parties to negotiate multilateral or bilateral agreements with the International Atomic Energy Agency for the application of its safeguards to its nuclear activities. These agreements are designed to ensure that the nuclear energy programs of the Contracting Parties are used exclusively for peaceful purposes.

The States Parties to the Treaty of Tlatelolco submit semiannual reports to OPANAL and to the International Atomic Energy Agency, for their information, stating that no activity prohibited under the Treaty has occurred in their respective territories (Article 14).

OPANAL has observer status at the United Nations General Assembly and participates yearly in the First Committee´s General Debate (Disarmament and International Security).

In addition, OPANAL has cooperation agreements with the following international organizations, academic institutions, and civil society organizations: Brazilian–Argentine Agency for Accounting and Control of Nuclear Materials (ABACC), Permanent Commission of the South Pacific (CPPS), Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), Latin American Institute of Educational Communication (ILCE), Nonproliferation for Global Security Foundation (NPSGlobal), International Atomic Energy Agency (IAEA), Latin American Energy Organization (OLADE), Latin-American Parliament (PARLATINO), the Secretariat of the Pacific Islands Forum (PIF), United Nations Regional Centre for Peace, Disarmament and Development in Latin America and the Caribbean (UNLIREC) and Soka Gakkai International.