How the treaty works

“Nuclear weapons have always been immoral. Now they are also illegal.”
– Setsuko Thurlow, Hiroshima atomic bomb survivor

Illegal Weapons

Nuclear weapons have always been immoral. Now they are also illegal in all respects under international law, with the entry into force of the Treaty on the Prohibition of Nuclear Weapons on 22 January 2021.

This landmark agreement – adopted at the United Nations in 2017 with the overwhelming support of the international community – is the first globally applicable treaty that categorically prohibits the most destructive, inhumane instruments of war ever created. It is also the first to put in place a framework for verifiably and irreversibly eliminating nuclear weapons, and for assisting the victims of their use and testing.

The treaty was born out of the deep concern of the world’s governments at the growing threat that nuclear weapons pose to human survival, the environment, socioeconomic development, the global economy, food security, and the health and welfare of current and future generations. They resolved to work together to challenge the dangerous status quo – and to bring the era of nuclear weapons to a permanent end.

The nuclear weapon ban treaty greatly strengthens the global taboo against the use and possession of nuclear weapons, rejecting the notion that these weapons are acceptable for some. History shows that the prohibition of certain types of weapons facilitates progress towards their elimination. Weapons that have been prohibited by treaties are increasingly seen as illegitimate, losing their political status and, along with it, the resources for their production.

Arms companies find it more difficult to acquire funds for work on illegal weapons, and such work carries a considerable reputational risk. Many major banks and other financial institutions have already begun divesting from nuclear weapon producers to comply with the new international law.

Underpinning the decision by governments and civil society to pursue the nuclear weapon ban treaty was the belief that changing the rules regarding nuclear weapons would have a profound impact even beyond those countries willing to join it at the outset. This belief stemmed from the experience with treaties prohibiting other inhumane weapons, which have established powerful norms that influence the policies and practices of holdout countries.

The nuclear weapon ban treaty offers the best hope of spurring long-overdue, meaningful action on nuclear disarmament.


Prohibited Activities

Article 1 of the Treaty on the Prohibition of Nuclear Weapons outlaws a wide range of nuclear-weapon- related activities. Countries that have joined it must never develop, test, produce, acquire, stockpile, transfer, use, or threaten to use nuclear weapons. They are also forbidden from hosting another country’s nuclear weapons on their territory or assisting or encouraging anyone else to engage in any of these prohibited activities. This article of the treaty draws on elements of the conventions banning chemical and biological weapons, anti-personnel landmines, and cluster munitions.

The treaty fills a major gap in international law. Prior to its entry into force, nuclear weapons were the only weapons of mass destruction not subject to a global ban treaty, despite the catastrophic, widespread, and persistent harm they inflict. While the Non-Proliferation Treaty of 1968 prohibits new countries from manufacturing nuclear weapons, it does not impose a general ban on the use or possession of nuclear weapons for all its parties, and the various nuclear-weapon-free zone treaties adopted since 1967 prohibit nuclear weapons only within particular geographic regions.

The nuclear weapon ban treaty is based on the rules and principles of international humanitarian law, which stipulate that the right of parties to an armed conflict to choose methods and means of warfare is not unlimited, that weapons must be capable of distinguishing between civilians and combatants, and that weapons causing superfluous injury or unnecessary suffering are prohibited.


Eliminating Nuclear Weapons

Article 4 of the Treaty on the Prohibition of Nuclear Weapons establishes a legal framework for the verified and irreversible elimination of nuclear weapons and their associated facilities. No other multilateral agreement provides such a framework.

Countries with nuclear weapons can opt to eliminate their weapons before joining the treaty, in which case an international authority must independently verify this. Alternatively, they can opt to join the treaty and eliminate their weapons in accordance with a time-bound plan. The treaty also includes a mechanism for ending the practice of “nuclear hosting”, whereby one country deploys another country’s nuclear weapons on its territory.

Countries must submit regular reports on the progress they have made in implementing these obligations until such time as they are fulfilled. Once a country has eliminated its nuclear weapons, it must accept stringent safeguards with the International Atomic Energy Agency (IAEA) to enable that body to verify that the disarmed country’s nuclear facilities and materials are never again used for weapon-related purposes.


Assisting Victims

The Treaty on the Prohibition of Nuclear Weapons is the first international agreement that requires countries to assist victims of the use and testing of nuclear weapons. They must also take measures towards remediating areas contaminated with radiation from nuclear explosions. These obligations are similar to those found in treaties that outlaw, and seek to mitigate the humanitarian harm caused by, anti-personnel landmines and cluster munitions.

Assistance to the victims of nuclear weapons can come in many forms, including medical care, rehabilitation, and psychological support. Countries must also provide for victims’ social and economic inclusion. These obligations apply not only to countries affected by nuclear explosions – all countries in a position to do so must render assistance where requested.

Nuclear weapons have been used twice in warfare, on the Japanese cities of Hiroshima and Nagasaki in 1945. Close to a quarter of a million civilians were incinerated in an instant or suffered agonising deaths in the weeks and months after the attacks. Many thousands more have died in the seven and a half decades since then from radiation-related illnesses.

Survivors, known in Japanese as “hibakusha”, have often required life-long treatment for severe burns, cancers, and other chronic illnesses. More than two thousand nuclear weapons have also been exploded since 1945 as part of test programmes – underground, underwater, and in the atmosphere – with devastating long-term impacts on human health and the environment. Many of the workers at test sites in various parts of the world, as well as communities living nearby or downwind, were exposed to high doses of radiation, resulting in cancers and other illnesses. Atmospheric tests inflicted the greatest harm.

As the preamble to the nuclear weapon ban treaty acknowledges, nuclear tests and related activities have had a disproportionate impact on indigenous peoples, whose lands, far away from the seats of power, were often selected for these deadly experiments. Women and children have also borne the brunt of nuclear explosions, being more vulnerable than men to the harmful effects of ionising radiation.


Bringing All Countries On Board

Any country may choose to join the Treaty on the Prohibition of Nuclear Weapons at any time. By signing the treaty, a country indicates its commitment to become a party to it in the future. By ratifying it, the country formally consents to be legally bound. Ratification can be a lengthy process, and typically requires the approval of the national legislature.

Support for the treaty will continue to increase over time as its norms become more deeply entrenched and pressure to conform to them intensifies. Some countries that were initially reluctant to come on board – whether because they feared the opprobrium of their allies or they clung to the misguided belief that nuclear weapons bring security – will eventually feel compelled to reassess their position as the treaty’s membership grows larger, and as more and more of their parliamentarians and citizens demand action.

This has been the case for other treaties. For example, France and China opposed the Non-Proliferation Treaty when it was negotiated in 1968 but resolved to join it decades later. The world is rapidly changing, and today’s leaders will not remain in power forever.

Countries that have joined the nuclear weapon ban treaty are required under Article 12 to encourage all other countries to join it, with the goal of attracting “universal adherence”. They can do this in many ways – for example, by making statements in support of the treaty at the United Nations, by raising it in their bilateral dealings with other countries, or by hosting regional workshops.


Why Join the Treaty

  • Nuclear weapons inflict devastation and suffering on a massive scale, threatening the very survival of humanity. Their use can never be justified. Joining the nuclear weapon ban treaty is a step that every country can – and must – take to help eliminate them globally.
  • The continued existence of several thousand nuclear weapons around the world undermines every country’s security. A moment of panic or carelessness, a bruised ego or misunderstanding, a computer malfunction or cyberattack could all too easily lead to catastrophe.
  • Nuclear weapons serve no legitimate military or strategic purpose. The nuclear weapon ban treaty offers the best hope of moving us rapidly towards a world that is permanently free of this menace.
  • Most countries have already joined treaties banning other categories of unacceptable weapons, including chemical and biological weapons, anti- personnel landmines, and cluster munitions. Joining the treaty banning nuclear weapons – which are by far the most destructive of all weapons – is a logical and necessary next step.
  • The treaty provides an essential legal foundation for verifiably eliminating nuclear weapon stockpiles and assisting the victims of their use and testing.
  • Countries that have joined the treaty are in a stronger position to insist that other countries comply with their non-proliferation and disarmament obligations. Joining the treaty sends a clear signal that the acquisition or indefinite retention of nuclear weapons is unacceptable. It helps stigmatise the weapons and put pressure on countries to eliminate them promptly.
  • Nothing in the treaty requires any country to withdraw from an existing military alliance. But all countries that have joined the treaty must ensure that they in no way assist or encourage their allies to engage in activities prohibited under the treaty.
  • An overwhelming majority of the world’s countries have indicated their support for this landmark treaty, which provides the basis for a more secure world for all. By joining it, your country will stand on the right side of history, the right side of the law, and the right side of humanity.


Making the Treaty Work

  • Political Advocacy: Urge parliamentarians in your country to declare their support for the nuclear weapon ban treaty by adding their names to the ICAN Parliamentary Pledge. Encourage them to ask questions in parliament and put forth motions directing the government to join the treaty.
  • Divestment: Hundreds of financial institutions – banks, pension funds, and insurance companies – invest in companies that help build and maintain nuclear arsenals. Call on these institutions to divest from such companies immediately, in line with the new international law.
  • Cities and Towns: Paris, Los Angeles, Barcelona, and Sydney ... these cities are among hundreds that have signed the ICAN Cities Appeal, calling on their governments to join the treaty. Ask your mayor and city council to get on board, including by ending all ties with nuclear weapon companies.
  • Universities: Many universities, especially in the United States, are involved in the research and design
    of nuclear weapons – largely in secret and in contradiction of their mission statements. Students and faculty must demand that they stop helping to build these illegal weapons.
  • Education: Universities and schools everywhere should teach their students about the ban treaty – and embrace a new way of thinking about nuclear weapons that focuses on the catastrophic humanitarian effects of their use and their incompatibility with international law.
  • Direct Action: Nuclear weapons are deployed at more than a hundred sites around the world, often without the knowledge – let alone consent – of nearby communities. Direct action can help expose your country’s support for illegal weapons and build pressure for disarmament.
  • Survivor Testimonies: A nuclear attack is almost too horrific to imagine. But take a moment to read the testimonies of the hibakusha – survivors of the US bombings of Hiroshima and Nagasaki. Then share the testimonies with others to raise awareness of the unspeakable violence of nuclear weapons.
  • Donating: Since 2007, ICAN has been campaigning to build a global groundswell of support for the total elimination of nuclear weapons. Your donation will help us continue our work around the world to bring every last country on board the nuclear weapon ban treaty.



"How the TPNW Works" (2021)