UN negotiating conference for the Treaty on the Prohibition of Nuclear Weapons, 2017


The Treaty on the Prohibition of Nuclear Weapons (TPNW) is an international treaty that was negotiated and adopted by a UN conference in 2017. The treaty, which provides a comprehensive prohibition of nuclear weapons, was the first multilateral disarmament treaty to be negotiated and adopted since the Convention on Cluster Munitions was adopted in 2008.

123 non-nuclear countries and one NATO (nuclear allied) country participated in the negotiating conference. None of the nuclear armed states participated. 122 of the participating countries supported the final negotiated treaty which was adopted on July 7, 2017. One non-nuclear state abstained. Netherlands (the participating NATO country) opposed.

The treaty was opened for signature and ratification in September 2017 and entered-into-force on January 22, 2021.

The treaty prohibits States parties from developing, testing, producing, acquiring, possessing, stockpiling, using or threatening to use nuclear weapons. The Treaty also prohibits the deployment of nuclear weapons on national territories of States parties, and the provision of assistance by States parties to any other State in the conduct of prohibited activities. States parties will be obliged to prevent and suppress any activity prohibited under the TPNW undertaken by persons or on territory under their jurisdiction or control.

The negotiations to achieve a Treaty on the Prohibition of Nuclear Weapons emerged from a series of international conferences on the humanitarian impact of nuclear weapons, and as one of the three recommendations from the 2016 UN Open Ended Working Group (OEWG) on Taking forward multilateral nuclear disarmament negotiations. (The other two recommendations of the 2016 OEWG related to progress on nuclear disarmament in the context of the NPT, and adoption of nuclear risk reduction measures and additional measures to take forward multilateral nuclear disarmament negotiations.)

The treaty is open for signature and ratification by any State.

The adoption of the treaty, and the large number of non-nuclear States that support it, provide a strong political push on the nuclear armed and allied states to take action. This is likely to increase once the treaty enters into force and the first Conference of States Parties is held.  

Questions and answers about the TPNW

Which countries support the Treaty?

As of June 2022, 86 non-nuclear countries had signed the TPNW, representing 27% of the world’s population and 30% of the world’s landmass. Of these, 62 had ratified the treaty making it legally binding on them. The United Nations is the depository for the Treaty. You can check which countries have signed and ratified at Status of the TPNW. Another 40 countries have indicated support for the TPNW through voting in favour of it at the UN General Assembly. Click here for the list of supporting countries. None of the nuclear-armed and allied states have supported, signed or ratified the treaty.  

Does the Treaty undermine the Non-Proliferation Treaty?
No – it supports the NPT and serves as part of NPT implementation by non-nuclear States

The preamble to the TPNW specifically supports the NPT. It reaffirms ‘the full and effective implementation of the Treaty on the Non-Proliferation of Nuclear Weapons, which serves as the cornerstone of the nuclear disarmament and non-proliferation regime, has a vital role to play in promoting international peace and security.’

Indeed, the TPNW not only supports the NPT, it can serve as an initiative in the implementation of Article VI of the NPT.  In 2020, the NPT States Parties adopted by consensus a final document of the NPT Review Conference which highlighted that all States parties, not only the nuclear-armed States, need to undertake initiatives to achieve a nuclear weapons-free world:

All States need to make special efforts to establish the necessary framework to achieve and maintain a world without nuclear weapons. The Conference notes the Five-Point Proposal for Nuclear Disarmament of the Secretary-General of the United Nations, which proposes inter alia the consideration of negotiations on a nuclear weapons convention or a framework of separate mutually reinforcing instruments backed by a strong system of verification

The TPNW could be seen as a good-faith measure by non-nuclear States to take forward their NPT disarmament obligations in light of the 2010 agreement.

There are some limits, however, to this interpretation. In 2015, a proposal for the NPT Review Conference to endorse the proposal for negotiations on a Treaty to Prohibit Nuclear Weapons was rejected by a number of States Parties to the NPT, and was one of the reasons for the Review conference failing to adopt a final document (the other main reason being disagreement on the way forward on establishing a Middle East Nuclear-Weapon-Free Zone). As such, there continue to be some States parties to the NPT who perceive the TPNW as undermining, rather than supporting, the NPT.   

Does the Treaty support, complement or undermine an incremental (step-by-step) disarmament approach?
Supports and complements.

In addition to supporting the NPT, the preamble of the TPNW supports the Comprehensive Test Ban Treaty and the establishment of regional nuclear-weapon-free zones. The TPNW is silent on other incremental nuclear disarmament measures such as arms reduction agreements, de-alerting, no-first use, prohibition of use, control of fissile material etc… However, a number of the leading countries in the TPNW are also active in initiatives which advance an incremental disarmament agenda including  the Stockholm Initiative and the Non-Proliferation and Disarmament Initiative.

Does the Treaty establish a legally binding and comprehensive ban on nuclear weapons?
Yes – but only for States parties

The treaty provides a legally binding prohibition of nuclear weapons for States parties. However, it does not apply to States that do not join the treaty. So far, only non-nuclear countries have joined the treaty, and none of the nuclear armed or allied states (those under extended nuclear deterrence relationships) have indicated that they are considering joining. So in effect the Treaty prohibits nuclear weapons for these States that do not have nuclear weapons, but does not apply to those who possess nuclear weapons or whose security includes reliance on nuclear deterrence, as they have not joined the treaty.  

The Treaty provides a relatively comprehensive ban on nuclear weapons for States parties. As indicated above it prohibits developing, testing, producing, acquiring, possessing, stockpiling, using or threatening to use nuclear weapons. The Treaty also prohibits the deployment of nuclear weapons on national territories of States parties, and the provision of assistance by States parties to any other State in the conduct of prohibited activities. However, the treaty does not specifically prohibit financing or transit of nuclear weapons. Proposals for the treaty to prohibit these two aspects were rejected in the negotiations.

In addition, the treaty includes very limited verification and compliance measures. It applys the IAEA safeguards, but no other measures for verifying compliance. It includes no specific enforcement measures. And unlike the treaties prohibiting nuclear testing and chemical weapons, the treaty establishes no agency to oversee treaty implementation. Rather it leaves this to the Conference of States Parties to determine.

Are there other legally binding bans on nuclear weapons?

The regional nuclear weapon free zones establish legally binding prohibitions on the possession of nuclear weapons by States parties in the zone, as well as protocols under which the nuclear-armed States accept legally binding prohibitions against the threat or use of nuclear weapons against States parties, and prohibitions of deployment of nuclear weapons on the territories of the States parties to the zones.

In addition, international humanitarian law and international law on the threat or use of force apply to nuclear weapons and are legally binding, as affirmed unanimously by the International Court of Justice in its Advisory Opinion on the Legality of the Threat of Use of Nuclear Weapons in 1996.

The universally binding nature of international humanitarian law was also affirmed by the States Parties to the NPT in 2010, in which the final agreed document expresses  ‘deep concern at the catastrophic humanitarian consequences of any use of nuclear weapons, and reaffirms the need for all States at all times to comply with applicable international law, including international humanitarian law.”

The ICJ concluded that, this law provides a general prohibition of the threat or use of nuclear weapons. The preamble of the TPNW affirms that any use of nuclear weapons would be in violation of this law.  

In addition, in October 2018 the UN Human Rights Committee affirmed in General Comment 36 that the threat or use of nuclear weapons is incompatible with the Right to Life – a right codified in Article 6 of the International Covenant on Civil and Political Rights (ICCPR). All of the nuclear armed and allied states are parties to the ICCPR (although China has not yet ratified it), and so the obligations affirmed in General Comment 36 apply to them all.

Does the Treaty help people and environments impacted by nuclear weapons testing and production?
Yes – but with some problems on responsibility

The Treaty obliges States parties to provide adequate assistance to individuals affected by the use or testing of nuclear weapons, as well as to take necessary and appropriate measure of environmental remediation in areas under its jurisdiction or control contaminated as a result of activities related to the testing or use of nuclear weapons. This is a very important part of the treaty, and distinguishes it from the Comprehensive Test Ban Treaty which includes no provisions to assist people or to restore environments which have been impacted by nuclear tests. The effects on human health from the radiation dispersed by nuclear testing, are severe and extremely long-lasting, impacting on past, present and future generations. The recognition of the human rights of people impacted and the need for environmental remediation is one of the high points in the adoption of this treaty.

However, there are some problems in the way the treaty allocates responsibility for addressing these impacts. The Treaty places the responsibility for assistance to impacted individuals and environmental remediation on the States which have jurisdiction over the individuals and environment impacted, not on the States who conducted the nuclear tests. In the case of Marshall Islands and Kazakhstan, for example, the tests were conducted by other countries who were exercising administrative authority over them (the USA and Russia respectively). In the case of the Marshall Islands, this might prevent accession to the treaty, even though they are a champion for nuclear disarmament, as they do not have the resources to meet such obligations.  

Does the Treaty provide a process for the elimination of nuclear weapons?
Yes – sort of

Article 4 of the Treaty provides a process for a State party to eliminate their stockpiles of nuclear weapons. The Conference of States Parties of the Treaty would establish a timeline for a State Party’s nuclear weapons to be removed from operational status and destroyed. Within 60 days of entry-into-force of the Treaty for a state party that possesses nuclear weapons, that state must submit its plan for complete elimination of its nuclear weapons to the other States Parties or to a ‘competent international authority’ designated by the States Parties. The Treaty also provides a process under Article 4 for designating a ‘competent international authority’ to verify the elimination of the nuclear weapons by a State prior to joining the Treaty, and a process for States Parties hosting nuclear weapons on their territories to remove these weapons and report on this removal to the UN Secretary-General.

A number of questions arise about this process including:

What would be the ‘competent international authority’ to verify the elimination of nuclear weapons? Would it be the UN Security Council, in which 5 nuclear armed states hold veto power, or the International Atomic Energy Agency which has expertise on fissile materials but not on nuclear weapons, or would the Conference of States Parties establish an agency for this purpose?

How would these provisions apply if none of the nuclear armed or allied States join the treaty? Would they be redundant? Are the nuclear armed and allied States more likely to follow a separate path to the prohibition and elimination of their nuclear arsenals?

What is a Nuclear Weapons Convention and how does it differ from the TPNW?
Main differences include proposed v existing agreement, who are States parties, verification, compliance, process for destruction and elimination of stockpiles, national implementation, reciprocity and entry-into-force.  

A Nuclear Weapons Convention (NWC), like the TPNW, would be a negotiated treaty on the prohibition and elimination of nuclear weapons. A key difference between them is that a NWC would require the participation of nuclear-armed States. The TPNW does not require this. Another key difference is that the TPNW has been negotiated and adopted. This gives it political value (see Key Value of the TPNW below). The NWC remains as a proposal. Negotiations on it have not yet commenced.

In 1996, the International Court of Justice concluded that the threat or use of nuclear weapons is generally illegal and that there is a universal obligation to negotiate and achieve the comprehensive elimination of nuclear weapons. The UN General Assembly responded by adopting a resolution which is repeated annually, calling for negotiations on a nuclear weapons convention which would provide for the prohibition of the development, testing, production, stockpiling, transfer, use and threat of use of nuclear weapons and providing for their elimination under strict and effective international control. UN Secretary-General Kofi Annan circulated a Model Nuclear Weapons Convention providing an outline on the technical, legal and political measures required to achieve this. UN Secretary-General Ban Ki-moon made the proposal for a Nuclear Weapons Convention a major focus of his 5-point proposal for nuclear disarmament.

Over 130 countries, including four nuclear-armed States, vote in favour of the nuclear weapons convention, but for the negotiations on it to commence participation of most of the nuclear-armed states would be necessary, including at least the five permanent members of the UN Security Council. In contrast, the TPNW was negotiated without the nuclear armed States and does not require their participation for it to enter-into-force.

The Model Nuclear Weapons Convention covers technical, legal and key political (security) issues of the nuclear armed States involving the prohibition and elimination of nuclear weapons so as to get their agreement. As such, it is much more detailed than the TPNW. It includes processes similar to those in the Chemical Weapons Convention, for the phased elimination of nuclear weapons stockpiles under strict and effective verification, compliance and enforcement. It also includes the principle of mutuality, i.e. acceptance and implementation of nuclear disarmament obligations by nuclear armed (and allied) States under the NWC is based on comparable acceptance and implementation by other nuclear-armed States.  The Model NWC also envisages a supporting resolution from the UN Security Council which would affirm the key NWC prohibitions against the threat and use of nuclear weapons as being binding international law, and would support the NWC timeframe for the complete elimination of nuclear weapons globally.

The TPNW was negotiated by non-nuclear States primarily as a result of their frustration at the failure of the nuclear-armed and allied states to start negotiations on a nuclear weapons convention or a package of agreements culminating in a nuclear weapons convention. Rather than continuing to wait for the nuclear-armed and allied States to negotiate a ban on nuclear weapons, the non-nuclear states have negotiated one themselves. The adoption of the treaty, and the large number of non-nuclear States that support it, provides a strong political push on the nuclear armed and allied states to take action. This is likely to increase once the treaty enters into force and the first Conference of States Parties is held.  

Are nuclear-armed States likely to join the treaty?

They did not join the negotiations. They are not likely to join a TPNW which requires them to unilaterally eliminate their weapons and forgo deterrence while other nuclear armed states remain outside of the regime and continue to possess, deploy and threaten to use nuclear weapons. Those nuclear armed States that are, or become, serious about nuclear elimination are much more likely to negotiate mutual nuclear disarmament agreements with other nuclear-armed states, or commence negotiations on a nuclear weapons convention which would provide a mutual process of global nuclear weapons prohibition and elimination. As mentioned above, four nuclear-armed States already support negotiations on a nuclear weapons convention, and others have indicated that this would be a feasible approach once political conditions allow.

What about the NATO and other allied States?
Possible for Australia. Unlikely for the rest, at least for now

NATO countries and other allied countries (Japan, South Korea and Australia) currently rely on nuclear deterrence as part of their security. In order to join the TPNW, they would need to relinquish nuclear deterrence.

For Australia, this would not be difficult. They are in a similar geo-strategic situation as their neighbour New Zealand which has relinquished its reliance on nuclear deterrence and joined the TPNW. The Austrlaian Labour Party, which won the most recent election (May 2022), had previously adopted a policy platform which includes giving serious consideration to join the TPNW. So there is a high possibility that Australia could join.  

For South Korea and Japan, it would be more difficult to forgo nuclear deterrence and join the TPNW due to nuclear threats from their neighbours (China, Russia and North Korea) which their extended nuclear deterrence policies are designed to counter. However, if the Korean peace process results in the adoption of a security arrangement like a North East Asia Nuclear Weapon Free Zone, which eliminates the nuclear threats to Japan and South Korea, they might then be able to join the TPNW.

NATO countries accept nuclear deterrence as part of their security. This is affirmed in the NATO Strategic Concept to which all NATO states must adhere. In order for a NATO state to join the TPNW, either the Strategic Concept would need to be changed, or the state would need to leave NATO.

Some TPNW advocates have argued that this is not the case, and that the Strategic Concept is not binding on NATO states. However, when New Zealand, a member of the ANZUS alliance, rejected nuclear deterrence, the other parties (USA and Australia) did not allow New Zealand to remain in the alliance, even though nuclear deterrence was a much less important factor in ANZUS than it is in NATO. The experience of New Zealand indicates that even if the nuclear deterrence policy in a nuclear alliance might not be legally binding, it is politically binding, at least for now.

In the negotiations for the TPNW, Netherlands made proposals that could have provided a possibility for NATO states to join the Treaty without having to leave NATO, and also which would have made it easier for other allied States to join the Treaty.

The most significant proposal was the ‘temporality clause’ which would have provided the possibility for states to sign and ratify the treaty, but add a condition where-by they immediately accept most of the obligations in the TPNW, but indicate one or more obligations they require time to be able to accept. This refers primarily to the Treaty prohibition on the threat of use of nuclear weapons, which NATO and other allied States are unable to adopt while remaining under extended nuclear deterrence relationships.

Netherlands proposed this as a ‘temporality clause’ and not a permanent reservation. As such, if it had been adopted in the Treaty, it would have established a commitment by any State enacting the clause on joining the Treaty to change (phase out) their national (and NATO) policies on nuclear deterrence. The fact that this was rejected by the TPNW negotiators, led to Netherlands voting against the final treaty, and locked in the barrier that the TPNW prohibition on threat of use of nuclear weapons provides to allied states joining the Treaty.

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