An Nuclear Weapons Free Zone(NWFZ) is a delimited geographical space where, through a treaty or convention, these weapons of mass destruction are prohibited.

La Resolution 3472 B of the United Nations General Assembly (UNGA) stipulates the main legally binding obligations of nuclear weapon States towards NWFZs and towards their member States:

1. Respect in all its parts the status of total absence of nuclear weapons defined in the treaty or convention that serves as the constitutive instrument of the zone;
2. Not contribute in any way to the practice of acts in the territories that are part of the zone that entail a violation of the aforementioned treaty or convention;
3. Do not use nuclear weapons and do not threaten their use against the member States of the zone.

There are five NWFZs currently in force on our planet: Latin America and the Caribbean (Treaty of Tlatelolco, opened for signature in 1967); South Pacific (Treaty of Rarotonga, 1985); Southeast Asian (Bangkok Treaty, nineteen ninety five); Africa (Treaty of Pelindaba, nineteen ninety six); Central Asia (Central Asian Treaty, 2006); and the territory of Mongolia, which in 2000 obtained international recognition as a nuclear-weapon-free state through the Resolution 55/335 S of the UNGA.

The Treaty for the Prohibition of Nuclear Weapons in Latin America and the Caribbean - known as the Treaty of Tlatelolco - is the legal instrument signed and ratified by all 33 countries in Latin America and the Caribbean whose purpose is to prohibit: the testing, use, manufacture, production, acquisition or deployment, by any means, of any nuclear weapon, directly or indirectly, within said region. It commits its Contracting Parties to use nuclear material and facilities under their jurisdiction exclusively for peaceful purposes (Article 1). In this way, the Treaty of Tlatelolco established the NWFZ of Latin America and the Caribbean.

The Treaty of Tlatelolco establishes its Zone of Application (Article 4); creates and structures the powers and regulates the activity of an Organization (OPANAL) that ensures compliance with the obligations of the Contracting Parties (Articles 6, 7, 8, 9, 10, 11, 19, 22 and 23); establishes a Control System in charge of OPANAL and the International Atomic Energy Agency (Articles 12, 13, 14, 15 and 16).

The Treaty contains two Additional Protocols, I and II, aimed, in the first case, at ensuring the status of military denuclearization of the territories that are in the Application Zone, de jure o de facto, under the control of extraterritorial States and, in the second case, includes the legally binding commitment of the States possessing nuclear weapons not to place their nuclear weapons within the Zone of Application of the Treaty, and not to use or threaten to use their nuclear weapons against any of the Contracting Parties.

The Latin American and Caribbean States, through the Treaty of Tlatelolco, seek: "to contribute to putting an end to the arms race, especially nuclear weapons, and to the consolidation of a world in 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 in Latin America and the Caribbean The following are Contracting Parties to the Treaty of Tlatelolco and, in turn, Member States of OPANAL: Antigua and Barbuda; Argentina; Bahamas; Barbados; Belize; Bolivia; Brazil; Chili; Colombia; Costa Rica; Cuba; Dominica; Ecuador; The Savior; Grenade; Guatemala; Guyana; Haiti; Honduras; Jamaica; Mexico; Nicaragua; Panama; Paraguay; Peru; Dominican Republic; Saint Kitts and Nevis; St. Vincent and the Grenadines; St. Lucia; Surinam; Trinidad and Tobago; Uruguay; and Venezuela.

It is made up of three organs: the General Conference; the Council; and the Secretariat led by a General Secretary.

The General Conference is the main Body of the Agency, it is made up of all Member States. It holds periodic meetings where it makes decisions about the operation and international agenda of OPANAL.

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

The Secretariat is made up of a Secretary General and the personnel he requires. The Secretary General holds office for a period of four years, and may be re-elected for a single additional period. In accordance with the decisions of the Conference and the Council, the Secretary General is in charge of ensuring the proper functioning of the Control System established by the Treaty of Tlatelolco.

By provision of Article 7 of the Treaty of Tlatelolco, the Headquarters of OPANAL are located in Mexico City. The address of the Agency is Calle Milton 61, Colonia Anzures, Alcaldía Miguel Hidalgo, CP 11590, Mexico City.

The Control System referred to in Article 12 of the Treaty of Tlatelolco is executed by two International Organizations: OPANAL and the International Atomic Energy Agency (IAEA). Article 13 of the Treaty commits the Contracting Parties to negotiate agreements - multilateral or bilateral - with the IAEA for the application of the latter's Safeguards to their nuclear activities. These agreements are intended 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 the IAEA declaring that no activities prohibited by the provisions of the Treaty have taken place in their respective territories (Article 14).

OPANAL has Observer status in the United Nations General Assembly and participates annually in the General Debate of the United Nations. First Committee (Disarmament and International Security) of said Assembly.

OPANAL also maintains 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 (CTBTO extension), Latin American Institute of Educational Communication (ILCE), International Atomic Energy Agency (IAEA), Latin American Energy Organization (OLADE), The Pacific Islands Forum (PIF) Secretariat, United Nations Regional Center for Peace, Disarmament and Development in Latin America and the Caribbean (UNLIREC), Nonproliferation Foundation for Global Security (NPSGlobal),Latin American Parliament (PARLATINO)  and Soka Gakkai International.