Treaty on the Prohibition of Nuclear Weapons

In February 2017 UN-mandated negotiations began on a treaty prohibiting the development, stockpiling and use of nuclear weapons. The first round of discussions, in March 2017, was a general exchange of views among participants, which included more than a hundred non-nuclear weapon states and a number of non-governmental organisations. Several countries, including all of the nuclear weapon states, boycotted the talks.

The second, and final, round of talks began on 15 June and concluded on 7 July 2017. Those talks eventually culminated in the adoption of a Treaty on the Prohibition of Nuclear Weapons (TPNW), which prohibits States Parties from developing, testing, producing, manufacturing, acquiring, possessing, stockpiling, transferring, or receiving control over nuclear weapons or other nuclear explosive devices. It also prohibits them from using, or threatening to use such weapons. States Parties are also required to prohibit and prevent the stationing, installation, or deployment of nuclear weapons on their territory or any other place under its jurisdiction or control. This latter provision has implications for those countries which have US nuclear weapons based on their territories: Belgium, Germany, Italy, the Netherlands and Turkey.

Entry into force 

122 countries voted in favour of the treaty. The treaty opened for signatures from any UN member state, regardless of their participation in the conference, on 20 September 2017. 

On 24 October 2020 Honduras became the 50th state to ratify the treaty, thereby allowing it to enter force. The treaty subsequently entered into force on 22 January 2021 and took full legal effect for those countries which had signed and ratified it by that date. The treaty currently has 61 States Parties and a further 25 signatories. It remains open to accession. 

To date, none of the nuclear weapon states have signed the treaty. Neither has any NATO Member State or country that falls under the US nuclear umbrella in Asia. 

What can the treaty achieve? 

Many critics have questioned what such a treaty will achieve if the nine nuclear states do not participate. Without signing and ratifying the treaty the nuclear states are not legally bound by its provisions and they are under no obligation to disarm. 

Consequently there are fears that the treaty will merely be symbolic and play no useful role in nuclear disarmament.  Advocates of the treaty argue, however, that it establishes an international norm which will, in the longer term, pressure the nuclear states, and their allies, to alter their perceptions and behaviour.  

First meeting of States Parties – June 2022 

On 21-23 June 2022 the first meeting of States Parties to the TPNW will take place in Vienna. The aim of that  meeting is to advance the implementation of the treaty’s provisions and examine ways to strengthen it. President-designate of that meeting, Alexander Kmentt, has said that one of the main aims was to convey that the treaty is a serious disarmament undertaking and to dispel the myth that the treaty in some way undermines the NPT. NATO countries Norway and Germany have said that they will participate in the meeting as observer states. 

Position of the British Government 

The British Government did not participate in the UN talks and will not sign and ratify the new treaty. It believes that the best way to achieve the goal of global nuclear disarmament is through gradual multilateral disarmament, negotiated using a step-by-step approach and within existing international frameworks, specifically the Nuclear Non-Proliferation Treaty. The Government has also made clear that it will not accept any argument that this treaty constitutes a development of customary international law binding on the UK or other non-parties.  

The UK will not participate as an observer state in the first meeting of States Parties later this month.