Published on 1 February 2026

Treaty on the Prohibition of Nuclear Weapons (TPNW)

The Treaty on the Prohibition of Nuclear Weapons (TPNW), negotiated in 2017, is a comprehensive ban prohibiting all parties to the treaty from developing, testing, producing, acquiring, possessing or stationing nuclear weapons on their national territory. Like most European countries, Switzerland has decided not to join the treaty, but will continue to participate as an observer in future meetings of States Parties.

Nuclear disarmament is making slow progress and a world without nuclear weapons still seems a long way off. This is one of the reasons that led to the Treaty on the Prohibition of Nuclear Weapons (TPNW) in 2017, which aims to curtail the legitimacy of possessing nuclear weapons by declaring them illegal, thus creating room for more far-reaching disarmament steps.

This approach was controversial from the start and accordingly, all states in possession of nuclear weapons and the majority of their allies stayed away from the negotiations.

Content of the TPNW

The treaty entered into force on 22 January 2021 and prohibits its member statesthe development, testing, production, transfer, possession, use, and threat of use of nuclear weapons. It also prohibits supporting, encouraging or inducing third parties to support activities that are prohibited to the states parties. Furthermore, states parties may not allow nuclear weapons to be stationed on their territory. The TPNW also contains commitments on victim assistance, environmental remediation resulting from nuclear testing or the use of nuclear weapons, and international cooperation in these areas.

The Swiss position on the TPNW

In 2017, Switzerland played an active part in the TPNW negotiations, issuing a statement on the outcome in an explanation of vote. In 2018, the Federal Council set up an interdepartmental working group to review the treaty and its implications. It concluded on balance that the reasons against accession outweighed the potential opportunities, considering among other things that the disarmament aspects of the TPNW were unclear.

In 2018 and 2019, the Federal Council decided to refrain from signing the TPNW for the time being. At the same time, however, it decided that Switzerland would take part in future intergovernmental conferences as an observer and would re-examine its position on the TPNW.

At the end of 2018, Parliament passed motion 17.4241: ‘Sign and ratify the Treaty on the Prohibition of Nuclear Weapons’. Based on this decision by Parliament, the Federal Council will review the question of accession with the assistance of external experts.

In September 2022, after the beginning of the war in Ukraine, the Parliament passed the postulate 22.3800 “Impact of Switzerland's accession to the Treaty on the Prohibition of Nuclear Weapons on Switzerland's foreign and security policy”.

In 2024, based on the working group's report and its report in response to postulate 22.3800, the Federal Council decided not to change its position. Switzerland will not access to the TPNW, but will continue to participate in meetings of States Parties as an observer. Domestically, further discussions on this treaty are ongoing, especially as civil society groups are collecting signatures for a referendum on joining the TPNW.

Regardless of the TPNW decision, Switzerland remains committed to disarmament. It continues to advocate for a world without nuclear weapons within the framework of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). The Federal Council continues to emphasise that the use of nuclear weapons would be hardly compatible with the obligations of international law, in particular international humanitarian law.

In March 2024, Switzerland also declared in the UN Security Council that a nuclear war cannot be won and must never be fought.

Switzerland is also strongly committed to the NPT implementation process and to nuclear risk reduction. It is also working to clarify the humanitarian consequences of nuclear weapons.

This differentiated, pragmatic commitment is also in line with the Federal Council's strategy on arms control and disarmament for 2022–2025.

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