Treaty of Tlatelolco: Nuclear-Weapon-Free Zone

Treaty of Tlatelolco: Nuclear-Weapon-Free Zone

Treaty of Tlatelolco: Nuclear-Weapon-Free Zone for Latin America and the Caribbean: The nuclear arms race and the 1962 Cuban Missile Crisis inspired Latin American governments to begin a process which would ensure that the region would never again become the scene of a nuclear conflict. These efforts culminated in the Treaty for the Prohibition of Nuclear Weapons in Latin America and the Caribbean (also known as the Treaty of Tlatelolco), which established the first Nuclear-Weapon-Free Zone (NWFZ) in a highly  populated area. The Treaty has been critical to advancing regional peace and security as well as creating a  precedent and inspiration for subsequent NWFZs and giving impetus to the universal elimination of nuclear weapons

In 2013, the Treaty of Tlatelolco received the top prize of the World Future Council’s annual Future Policy Award, which was held on the theme of disarmament, in partnership with the UN Office for Disarmament Affairs and the Inter-Parliamentary Union.

At a Glance
  • Set a fundamental legal precedent as the first agreement to successfully implement a fully-fledged, legally binding, nuclear-weapon-free zone (NWFZ).
  • Inspired other regions and countries to pursue a nuclear-free policy and has contributed to universal nuclear disarmament.
  • The only nuclear-weapon-free zone (NWFZ) that has a dedicated organisation to safeguard the principles of the treaty and ensure its goals are achieved.

Last Update: 2019


The Tlatelolco Treaty provides the Latin American and Caribbean States with the legitimacy to continue to promote their ultimate goal and one of today’s main global challenges, the achievement of universal nuclear disarmament.

Gioconda Úbeda Rivera, former Secretary-General of the Agency for the Prohibition of Nuclear Weapons in Latin America and the Caribbean (OPANAL) and Deputy Minister of Foreign Affairs of Costa Rica

Policy Reference

Treaty for the Prohibition of Nuclear Weapons in Latin America and the Caribbean (Treaty of Tlatelolco), 1967. [English]

Connected Policies

Additional Protocol 1 binds overseas countries with territories in the region to the terms of the treaty. [English]

Additional Protocol 2 binds the world’s declared nuclear weapons states from undermining the nuclear-free status of the region. [English]

Other Nuclear-Weapon-Free Zones

Treaty of Rarotonga — South Pacific Nuclear-Weapon-Free Zone [English]

Treaty of Bangkok — Southeast Asia Nuclear-Weapon-Free Zone [English]

Treaty of Pelindaba — African Nuclear-Weapon-Free Zone [English]

Treaty of Semipalatinsk – Central Asia Nuclear-Weapon-Free Zone [English]

Selection as a Future-Just Policy

After the Cuban Missile Crisis brought a nuclear conflict to the doorstep of Latin America, the Treaty of Tlatelolco was designed to improve the security of current and future generations from the devastating and potentially irreversible consequences of a nuclear conflict in the region.

It is far-sighted treaty which has prevented the ‘horizontal spread’ of nuclear weapons in the region as some of the larger states began to develop nuclear energy industries, which could have provided capacity for the future development of nuclear weapons.

The treaty’s multilateral framework and confidence-building measures have contributed to the emergence of a consensus favouring non-proliferation and peaceful conflict resolution principles in the region.

Future-Just Policy Scorecard

Our “Best Policies” are those which meet the Future-Just Lawmaking Principles and recognise that interrelated challenges require interconnected solutions. The World Future Council’s unique research and analysis ensures that important universal standards of sustainability and equity, human rights and freedoms, and respect for the environment are coherently considered by policy-makers.

   Sustainable use of natural resources

  • Recognising an existential threat, the treaty preamble emphasises that “nuclear weapons (…) constitute, through the persistence of the radioactivity they release, an attack on the integrity of the human species and ultimately may even render the whole earth uninhabitable.
  • By preventing nuclear war, and contributing to normative efforts to eliminate nuclear weapons regionally and globally, the Treaty of Tlatelolco has helped avoid devastating environmental consequences.
  • The treaty not only serves to reduce the risk of nuclear war within the region but also functions to prevent the testing of nuclear weapons, long associated with adverse health and environment effects.

   Equity and poverty eradication

  • The treaty has contributed to the security of current and future generations from the potentially irreversible consequences of a nuclear conflict in the region. Such consequences may include economic collapse, intense suffering and poverty amongst the affected populations and the creation of massive numbers of refugees.
  • The preamble explicitly recognises that “The existence of nuclear weapons in any country of Latin America would make it a target for possible nuclear attacks and would inevitably set off, throughout the region, a ruinous race in nuclear weapons which would involve the unjustifiable diversion, for warlike purposes, of the limited resources required for economic and social development.”

   Precautionary approach

  • The Tlatelolco framework embodies the precautionary principle in its essence by preventing the use of technical and scientific capacities to develop or deploy a type of weapon of mass destruction which would pose incalculable risks of devastating destruction to the peoples and environments of the region, as well as trans-boundary consequences for other regions and the world.

   Public participation, access to information and justice

  • Though the Tlatelolco Treaty was initiated and concluded amongst foreign policy diplomats to the general exclusion of civil society groups, it does contain mechanisms for public participation, including access to information and avenues for redress.
  • The Agency for the Prohibition of Nuclear Weapons in Latin America and the Caribbean (OPANAL) carries out public education and awareness campaigns on nuclear weapons and facilitates online access to information.
  • OPANAL also organises conferences attended by civil society representatives, as well as experts, concerned about nuclear risks.

    Good governance and human security

  • The Tlatelolco Treaty has the most advanced and developed organisational framework for the implementation and monitoring of the treaty provisions of all the existing regional NWFZ. It is overseen by the General Conference, the supreme body of OPANAL which meets every two years, as well as a Council and a Secretariat.
  • OPANAL has responsibility for the “holding of periodic or extraordinary consultations among Member States on matters relating to the purposes, measures and procedures set forth in the Treaty and to the supervision of compliance with the obligations arising thereform” (Article 7(2)). The Treaty also includes effective provisions for measures to deal with treaty violations and settlement of disputes.
  • Accountability is provided for by Article 14 of the treaty which order states to submit reports to OPANAL, the International Atomic Energy Agency (IAEA) and the Organization of American States (OAS).
  • Article 20 allows for the General Conference to make recommendations as it deems appropriate on treaty violations, and if a violation is considered likely to endanger peace and security, the General Conference can refer the violation to the UN Security Council and UN General Assembly through the UN Secretary-General, as well as to the Council of the OAS, and to the IAEA.
  • In the event of non-agreement on peaceful settlement of a dispute, Article 24 allows for a referral to the International Court of Justice.

   Integration and interrelationship

  • The treaty both reflects and contributes to regional cooperation in Latin America with regards to the prevention of nuclear weapon proliferation and nuclear attack, whether arising from within the region or through the nuclear deployments of external powers.
  • Inter-agency cooperation is embodied in its treaty provisions and includes the IAEA, the UN Security Council, the UN General Assembly, the UN Secretary-General, and the OAS.
  • Article 13 requires all parties to enter into safeguard agreements with the IAEA, and OPANAL is required to make regular reports to the IAEA and the OAS.

   Common but differentiated responsibilities

  • The treaty imposes the same obligations on all regional parties and serves to reduce potential inequalities in states which might have otherwise diverted some of their resources and economic development into nuclear weapon research, development and production.
  • The treaty is consistent with, and sensitive to, the level of technology and scientific knowledge of many countries in the region with regards to nuclear energy production.
  • The Treaty implicitly takes into account regional history (such as the Cuban Missile Crisis) where nuclear weapons were stationed in the region to the potential detriment of its security. The preamble notes that “the existence of nuclear weapons in any country of Latin America would make it a target for possible nuclear attacks.”


Initial efforts to create an area free of nuclear weapons began in the late 1950s with several proposals to establish such a zone in Central and Eastern Europe. Poland offered the first proposal – named the Rapacki Plan after the Polish foreign minister – in 1958. The Soviet Union, Sweden, Finland, Romania, and Bulgaria also floated similar proposals. All these early efforts, however, floundered amidst the US-Soviet superpower conflict.

In the same year, Costa Rica was the first in the region to (unsuccessfully) propose a Latin American nuclear arms control arrangement during a meeting of the OAS Council. In 1960, French nuclear weapon testing in the Sahara, together with the South African apartheid regime’s interest in nuclear arms, led African states to issue a call for a NWFZ, as endorsed by the UN General Assembly the year after. Alone amongst Latin American states, Brazil supported the African NWFZ resolution and proposed a similar zone within its own region.

By 1962, the growing nuclear arms race that had begun at the end of World War II, together with the nuclear stand-off between the United States and the Soviet Union, came to a head with the Cuban Missile Crisis.  Latin-American governments pushed themselves to ensure that the region would never again become the setting for nuclear conflict.

In 1963, the efforts of Alfonso Garcia Robles, the Mexican ambassador to Brazil, eventually led to Bolivia, Brazil, Chile, and Ecuador joining Mexico in supporting a Latin American NWFZ. The Treaty of Tlatelolco was carefully negotiated in Mexico City between 1964 and 1967, and Alfonso García Robles ultimately received the Nobel Peace Prize for his efforts in this process.

On February 14th 1967, the Treaty for the Prohibition of Nuclear Weapons in Latin America and the Caribbean (the Treaty of Tlatelolco) was signed. Two years later, the Agency for the Prohibition of Nuclear Weapons in Latin America and the Caribbean (OPANAL) was created in order to safeguard the treaty principles and ensure the achievement of its goals. It was the first NWFZ established in a highly populated area (the 1959 Antarctic Treaty had demilitarised Antarctica). Today the treaty counts all 33 States of Latin America and the Caribbean as members.


The Treaty of Tlatelolco was designed to achieve a number of objectives, namely:

  • To ensure peace and security in Latin America and the Caribbean through military denuclearisation of the region.
  • To contribute to halting the nuclear arms race, by preventing the proliferation of nuclear weapons and making a lasting contribution towards general and complete (nuclear) disarmament.
  • To ensure that limited resources are not diverted to nuclear armaments but instead allocated to economic and social development.
  • To strengthen peaceful conflict resolution principles and consolidate a “permanent peace” in accord with the UN Charter and the Charter of the Organization of American States.
  • To strengthen the application of international law and implement its fundamental principles.
  • To act as a point of reference and source of inspiration for the creation of subsequent NWFZ.

Methods of Implementation

The Treaty of Tlatelolco aims to prohibit and prevent:

(a) the testing, use, manufacture, production, or acquisition by any means whatsoever of any nuclear weapons, by the Parties themselves, directly or indirectly, on behalf of anyone else, or in any other way; and

(b) the receipt, storage, installation, deployment, and any form of possession of any nuclear weapons, directly or indirectly, by the Parties themselves, by anyone on their behalf, or in any other way. The Parties also undertake to refrain from engaging in encouraging or authorizing, directly or indirectly, or in any way participating in the testing, use, manufacture, production, possession, or control of any nuclear weapons.

Article 1, Treaty

Additional Protocol 1 binds overseas states with territories in the region, while Additional Protocol II requires nuclear weapon non-use and non-threat of use from the five official nuclear-weapon-states (US, UK, France, Russia and China).

The Agency for the Prohibition of Nuclear Weapons in Latin America (OPANAL) is the regional agency tasked with monitoring, verification, compliance and wider education on the need for nuclear disarmament whilst the General Conference is its supreme organ.

It is appropriate to see the Treaty, the Additional Protocols I and II and OPANAL as collectively making up the ‘Tlatelolco System,’  a dynamic and evolving architecture influenced by OPANAL’s continuing engagement and initiatives.


The Treaty of Tlatelolco was the first to successfully implement a fully-fledged, legally binding, nuclear-weapon-free zone policy seeking to ensure the absence of nuclear weapons from the whole of Latin America.

The Treaty’s objectives were both timely in terms of addressing the immediate threat posed by the ‘vertical spread’ of nuclear weapons into the region from external nuclear powers, and foresighted in preventing a ‘horizontal spread’ of nuclear weapons within the region. Some of the larger states in the region had begun to develop nuclear energy industries, providing an opportunity for the future development of nuclear weapons.

The Tlatelolco Treaty has successfully reduced the risk of nuclear weapon proliferation within Latin America and the risk of becoming a target in a nuclear conflict involving external powers. Not only has it successfully secured legally binding undertakings from all regional states not to acquire or develop nuclear weapons, it has also created verification and monitoring frameworks, as well as regional forums, that have generated trust and cooperation in regional disarmament efforts. It  also contributed to the reversal of military control of nuclear energy programs in Argentina and Brazil – two Latin American countries with the most developed nuclear industries.

The Tlatelolco Treaty played, and continues to play, a critical role in the development of regional non-proliferation norms. Its multilateral framework was a catalyst for Argentine-Brazilian nuclear rapprochement while its negotiation, creation and subsequent implementation has played a key role in the emergence of a consensus favouring non-proliferation in the region.

The Latin American region is now one of the most secure in the world from a regional nuclear conflict and most able to deploy its economic capacity and resources for peaceful economic development rather than expending them on unproductive nuclear arms races that only serve to undermine regional security.

The treaty has been particularly successful in gaining legally binding ratification from all 33 countries in the Latin American region. This includes countries, such as Argentina and Brazil, with highly developed nuclear industries, as well as the one country which had hosted nuclear weapons from an external nuclear weapon state, Cuba – the last to accede in 2002.

The Tlatelolco Treaty has also been uniquely successful in gaining legally binding all five of the official nuclear weapon states recognised in the The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) not to use, or threaten to use, nuclear weapons against Latin American states party to the treaty. None of the other four NWFZs in populated regions have yet to secure such adherence from all five of the nuclear weapon states.

The Agency for the Prohibition of Nuclear Weapons in Latin America (OPANAL) has furthermore been successful in promoting the Treaty around the world and strengthening cooperation between all states belonging to nuclear-weapon-free zones, e.g. through conferences. There have been three such conferences which have served to promote wider nuclear elimination approaches in both UN and NPT review forums.

Finally, the treaty acts as an example which could encourage similar regional denuclearisation measures and contribute to the impetus for global nuclear weapon elimination. As one of the architects of the Treaty, Mexico’s Nobel-Prize-winning Ambassador Alfonso Garcia Robles, explained: “It provides profitable lessons for all States wishing to contribute to the broadening of the areas of the world from which those terrible instruments of mass destruction that are nuclear weapons would be forever proscribed.”

Tlatelolco was more than a nuclear non-proliferation initiative or a regional NPT. The assertion of regional commonality against non-regional interference was a central motivating factor of Tlatelolco, and continues to give the agreement particular importance to the parties. It contained a unique waiver mechanism (Article 28) that enabled the gradual take-up of regional non-proliferation norms in a context where there are some initially hesitant states. This allowed states to bring the treaty into force for their own territories ahead of the wider objective of having the treaty in force for the whole of Latin America by waiving certain provisions and to allow the treaty to enter into force for their territory only.

In the declaration of 26 September 2019, on the International Day for the Total Elimination of Nuclear Weapons, Member States declared to “reaffirm the importance of the ‘United Nations study on disarmament and non-proliferation education’ adopted by Resolution 57/60 of the United Nations General Assembly, in its LVII Session2 (2002) and commit themselves to continue working on the implementation of programs of education programs on nuclear disarmament and non-proliferation, convinced that they are an effective means to contribute to the consolidation of international peace and security.”[1]

In UNGA Resolutions 57/60 of 22 November 2002, 59/93 of 16 December 2004, 61/73 of 3 January 2007, 63/70 of 12 January 2009, 67/77 of 8 December 2010, 67/47 of 3 December 2012, 69/65 of 2 December 2014, 71/57 of 5 December 2019, 73/59 of 13 December 2018 it is recognized the importance of promoting concerted international efforts at disarmament and non-proliferation, in particular in the field of nuclear disarmament and non-proliferation, with a view to strengthening international security and enhancing development, at the time of furthering the implementation of the recommendations of the United Nations study. [2]

They created a few great things:

– The online course The Nuclear Challenge” – through Resolution CG/Res.518 of 26 November 2009, was launched for government officials, political advisors, lawmakers, members of the armed forces of the Member States. The course was held from 2009 to 2012, the first three conducted in Spanish and the last one in English.

– The course “Education for Nuclear Disarmament and Non-Proliferation” was implemented at the XXIII Special Session held on 19 November 2014. The General Conference took note of the recommendations of the GTE contained in its report SG.14.2014 and through Resolution CG/E/Res.576, the mandate of the GTE was extended in order to explore new possibilities. From 2017 to 2019, there have been four editions of the Course on Disarmament and Non- Proliferation. All four editions of the Course on Disarmament and Non-Proliferation have been conducted with the supported of Ambassador Sergio de Queiroz Duarte, former United Nations High Representative for Disarmament Affairs and current President of Pugwash Conferences on Science and World Affairs.

Among its activities for disarmament and non-proliferation education, the Secretariat of the Agency has welcomed students as part of the Internship Program.

At the 288th Meeting of the Council held on 19 June 2014, it was decided to associate the Agency to the “Summer School on Nuclear Disarmament and Non-Proliferation”, in which diplomats from the region participate, and which is co-organized by the Matías Romero Institute and the James Martin Center for Nonproliferation Studies. At the 320th Meeting of the Council held on 27 June 2019, the representative of Mexico announced that the sixth edition of the Summer School would be postponed until 2020.

[1] Education for disarmament and non-proliferation of nuclear weapons (2019), Opanal General Conference, XXVI Session CG/17/2019 7 November 2019 Item 8, OPANAL – Agency for the Prohibition of Nuclear Weapons in Latin America and the Caribbean

[2] Education for disarmament and non-proliferation of nuclear weapons (2019), Opanal General Conference, XXVI Session CG/17/2019 7 November 2019 Item 8, OPANAL – Agency for the Prohibition of Nuclear Weapons in Latin America and the Caribbean

Potential as a Transferable Model

The significance of the Tlatelolco Treaty as a legal precedent, an example of multilateral cooperation and inspiration to other regions, is indicated by the fact that 91 UN member states, almost half of the whole UN, have now ratified legally binding regional nuclear-weapon-free-zone treaties, based on varying degrees  on the Tlateloco model. The entire Southern Hemisphere is now denuclearized.

Regions currently covered by nuclear-weapon-free zones, in addition to Latin America and the Caribbean, are the South Pacific, South-East Asia, Africa and Central Asia. In addition, Mongolia has established itself as a single-state NWFZ.

Each NWFZ Treaty is different and has elements with potential for transferability. Although the Treaty of Tlatelolco has limitations and shortcomings – e.g. it doesn’t prohibit the dispersal of nuclear waste in the zone and it leaves some room for ambiguity with regard to “peaceful nuclear explosives” – the influence of the precedent-setting nature of the first nuclear-weapon-free zone in a populated area is self-evident. Its most fundamental aspects have served as a model for and have been replicated in other NWFZ treaties.

Some of the elements with the potential for transferability include:

  • Elements of general prohibition of nuclear weapons.
  • An additional protocol binding the five NPT-recognised nuclear-weapon states – China, France, the Russian Federation, the United Kingdom and the United States.
  • The phased entry-into-force and waiver mechanism, which allows for flexible implementation of the treaty.
  • The creation of a administrative agency, which can coordinate actions on behalf of Member States and promote the ideals of the Treaty in international fora.

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