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The 50th ratification of the Treaty on the Prohibition of Nuclear Weapons

Book of signatures at signing of TPNW
Signing ceremony for Treaty on Prohibition of Nuclear Weapons. The Treaty, which was adopted on 7 July 2017 by 122 states, opened for signature on 20 September, on the sidelines of the annual general debate of the General Assembly. Photo: Flickr/UN Photo/Kim Haughton.

Yesterday Honduras became the 50th state to ratify or accede to the 2017 Treaty on the Prohibition of Nuclear Weapons (TPNW), meaning that the treaty will enter into force on 22 January 2021. The TPNW is the first multilateral treaty to clearly define the possession, use or threatened use of nuclear weapons as illegal under international law.

‘The TPNW sets out a noble aspiration,’ says Ambassador Jan Eliasson, Chair of the SIPRI Governing Board. ‘Only a nuclear-free world can be free of the risk that a nuclear weapon will be used one day, raising the prospect of a humanitarian catastrophe of unimaginable proportions. That was the starting point for this treaty for governments and civil society organizations.’

‘All the nuclear weapon states are upgrading their arsenals,’ adds Dan Smith, SIPRI Director. ‘And arms control is in crisis. The strategic arms agreement between Russia and the United States—the last bilateral arms control treaty still standing—must be extended by February next year. It is not surprising that a radical change of direction is gaining this degree of support worldwide.’

The TPNW was adopted in July 2017 at a special United Nations conference. States parties undertake not to develop, test, produce, acquire, possess, stockpile, use or threaten to use nuclear weapons. The treaty also prohibits the deployment of nuclear weapons on national territory and assistance to any state in the conduct of prohibited activities. The treaty has not been signed by any of the nuclear weapon-possessing states.


Ambassador Jan Eliasson is a Distinguished Associate Fellow at SIPRI.
Dan Smith is the Director of SIPRI.