Japan
Japan boycotted the negotiations on the Treaty on the Prohibition of Nuclear Weapons (TPNW) in 2017 and has consistently voted against the annual UN General Assembly resolutions on the Treaty, including in 2025. The government has faced mounting criticism domestically for continuing to claim reliance on the US ‘nuclear umbrella’ and refusing to engage with the TPNW. Japan may sign and ratify or accede to the TPNW, but will have to make changes to its policies and practices to become compliant.
TPNW Status
| Key weapons of mass destruction treaties | ||
|---|---|---|
| NUCLEAR WEAPONS | ||
| Party to the TPNW | No | |
| Party to the NPT | Yes (Ratified 1976) | |
| Ratified the CTBT | Yes (Ratified 1997, Annex 2 state) | |
| Party to an NWFZ | No | |
| CSA with the IAEA | Yes (In force 1977) | |
| AP with the IAEA | Yes (In force 1999) | |
| BIOLOGICAL AND CHEMICAL WEAPONS | ||
| Party to the BWC | Yes (Ratified 1982) | |
| Party to the CWC | Yes (Ratified 1995) | |
| TPNW Art. 1(1) prohibitions: Compatibility in 2025 | ||
|---|---|---|
| (a) | Develop, produce, manufacture, acquire | Compatible |
| Possess or stockpile | Compatible | |
| Test | Compatible | |
| (b) | Transfer | Compatible |
| (c) | Receive transfer or control | Compatible |
| (d) | Use | Compatible |
| Threaten to use | Compatible | |
| (e) | Assist, encourage or induce | Non-compatible |
| (f) | Seek or receive assistance | Compatible |
| (g) | Allow stationing, installation, deployment | Compatible |
| TPNW voting and participation | |
|---|---|
| UNGA resolution on TPNW (latest vote) | Voted no (2025) |
| Participated in 3MSP (2025) | No |
| Participated in 2MSP (2023) | No |
| Participated in 1MSP (2022) | No |
| Average MSP delegation size (% women) | N/A |
| Adoption of TPNW (7 July 2017) | N/A |
| Participated in TPNW negotiations (2017) | No |
| Negotiation mandate (A/RES/71/258) | Voted no |
| Fissile material | |
|---|---|
| Nuclear facilities | Yes |
| Fissile material production | Yes (Civilian) |
| HEU stocks | 1-10 tons |
| Plutonium stocks | 45.1 Mt (9.2 Mt in Japan) |
| SQP with the IAEA | No |
Latest developments
Japan’s decision not to attend the Third Meeting of States Parties (3MSP) to the Treaty on the Prohibition of Nuclear Weapons (TPNW) as an observer in March 2025 sparked strong criticism from atomic bombing survivors, including representatives of Nihon Hidankyo, the organization that won the 2024 Nobel Peace Prize.1
In defending the government’s decision, the then-Minister of Foreign Affairs of Japan, Takeshi Iwaya, argued: ‘Nuclear deterrence is indispensable. The TPNW is incompatible with nuclear deterrence. If our country attends the meeting as an observer nation, it could send a wrong message about our country’s nuclear deterrence policy and cause problems in securing peace and security.’
In the general debate of the 80th session of the UN General Assembly in September 2025, the then-Prime Minister of Japan, Shigeru Ishiba, said: ‘We must address the issue of nuclear weapons head on. We are fully aware of the domestic and international calls on Japan to join the [TPNW], as the only country to have suffered atomic bombings. However, we must maintain a world without nuclear war and also realize a world without nuclear weapons. To this end, the NPT, which brings together both nuclear-weapon States and non-nuclear-weapon States, is the most effective and realistic framework.’2
After leaving office, he expressed regret that Japan opted not to observe 3MSP under his leadership.3
Shigeru Ishiba’s successor, Sanae Takaichi, has reportedly contemplated revising Japan’s ‘three non-nuclear principles’, which forbid the country from producing or acquiring nuclear weapons or hosting foreign nuclear weapons. In February 2026, however, she said that her government would uphold the principles, rejecting the idea of a nuclear-sharing arrangement with the United States similar to that in place with European NATO members.4
In December 2025, 117 Japanese lawmakers expressed their support for Japan’s signature and ratification of the TPNW in a survey conducted by Nihon Hidankyo.5
Recommendations
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Japan should renounce the possession and potential use of nuclear weapons on its behalf, and ensure that nuclear weapons do not have a role in its defence posture.
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Japan should comply with its existing obligation under Article VI of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and pursue negotiations in good faith on nuclear disarmament.
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Japan should urgently adhere to the TPNW. Until it is in a position to do so, it should welcome the TPNW as a valuable component in the global disarmament and non-proliferation architecture, work with the Treaty's states parties on practical steps towards disarmament, and attend the meetings of states parties as an observer.