From Wikipedia:

The Treaty on the Prohibition of Nuclear Weapons (TPNW), or the Nuclear Weapon Ban Treaty, is the first legally binding international agreement to comprehensively prohibit nuclear weapons with the ultimate goal being their total elimination. It was adopted on 7 July 2017, opened for signature on 20 September 2017, and will enter into force on 22 January 2021.[3][4][5][6]

For those nations that are party to it, the treaty prohibits the development, testing, production, stockpiling, stationing, transfer, use and threat of use of nuclear weapons, as well as assistance and encouragement to the prohibited activities. For nuclear armed states joining the treaty, it provides for a time-bound framework for negotiations leading to the verified and irreversible elimination of its nuclear weapons programme.

A mandate adopted by the United Nations General Assembly on 23 December 2016 scheduled two sessions for negotiations: 27 to 31 March and from 15 June to 7 July, 2017.[7] The treaty passed on schedule on 7 July with 122 in favour, 1 against (Netherlands), and 1 official abstention (Singapore). 69 nations did not vote, among them all of the nuclear weapon states and all NATO members except the Netherlands.[8]


No nuclear-armed nation has expressed support for a ban treaty; indeed, a number of them, including the United States[54] and Russia,[55] have expressed explicit opposition. North Korea was the only nuclear state to vote for initiating ban negotiations.[23][24][better source needed]

Many of the non-nuclear-armed members of the North Atlantic Treaty Organization (NATO), along with Australia[56] and Japan,[57] are also resistant to a ban treaty, as they believe that US nuclear weapons enhance their security.[50] A statement was put forward by several NATO members (not including France, the United States, nor the United Kingdom, the nuclear weapon states within NATO), claiming that the treaty will be 'ineffective in eliminating nuclear weapons' and instead calling for advanced implementation of Article VI of the Non-Proliferation Treaty.

Parties and signatories

As of 25 October 2020, 84 states have signed the Treaty and 50 states have ratified or acceded(a) to it.


From "What The Nuclear Ban Treaty Means For America's Allies":

At present, the risks of joining the Treaty on the Prohibition of Nuclear Weapons seemingly outweigh its potential benefits for NATO members, and NATO members remain committed to maintaining a nuclear alliance. The impact and longevity of the treaty will ultimately depend on how its members and supporters address numerous questions about its implementation, including those raised here — alignment with NATO membership, compliance, universality, relationship with the Nuclear Non-Proliferation Treaty, and practical concerns around member dues and convening. These are hefty questions for the first meeting of states parties of the nuclear ban treaty.


The text of the treaty itself.


Subquestions I'm curious about, for your inspiration:

  • Will at least one nuclear state give up nukes due to this treaty by 2035? (or any year you choose)
  • How many states will join the treaty by 2035?
  • How many nuclear states will join the treaty by 2035?
  • What are the chances a member state will go on to develop nuclear weapons?
  • Will a NATO member join the treaty by 2035?
  • What is the probability that the U.S., Russia, or China specifically will join the treaty by 2030, 2050?
  • What is the base rate of adoption for international weapons ban treaties?
  • What is the base rate of success at compliance & enforcement for international weapons ban treaties?
  • Will the treaty be enforced against specific member states?
  • What are the chances that member states of the treaty will withdraw?
  • Will the treaty be elaborated on its details, as its advocates intend?
  • Will this mess up deterrence and cause more nuclear instability on the margin?
  • How game-theoretically sound is this? What equilibria can/will most likely come out of this? (Relatedly: Is Global Zero game-theoretically stable in some instantiations? What about Global "A Small Number Of Nukes Remaining For Defensive Purposes"?)
  • How much has existential risk been reduced or increased by this?

For additional forecasting reference, here is a link to all of the Metaculus questions involving nukes.

Written with helpful contributions from Matthew Barnett.


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3 comments, sorted by Highlighting new comments since Today at 11:14 AM

You may be interested in "Will the Treaty on the Prohibition of Nuclear Weapons affect nuclear deproliferation through legal channels?" by Luisa Rodriguez, then at Rethink Priorities.

Rethink Priorities recently hired a new researcher, Michael Aird, who will resume work on looking into this treaty.

Yeah, as Peter says, this is something I'll start focusing on in a few months (there's ~1 other nuclear risk research project I'll work on first). So I hope to have at least one writeup on this for Rethink in 2021. And if people are knowledgeable about or interested in this treaty or related matters, feel free to reach out to me.

For now, I'd second Peter's recommendation of that post by Luisa.

I'd be curious to hear if there's a particular reason you (DonyChristie) and Matthew are interested in this question?

ETA: Also, thanks (to DonyChristie) for linking to those Metaculus questions - I hadn't had a look for relevant questions on Metaculus yet, but now I think these might be fairly useful to a bunch of my upcoming work, and I'll probably add some additional questions later.

When I originally got an email from Ploughshares Fund about it, the headline was suggestive of nukes everywhere being banned. This seemed like a probably-wrong impression to me. Nevertheless, I contended with a possible reality in which nuclear war suddenly was no longer a problem. I grappled with just how worthy of ecstatic celebration this would be; social norms do not suggest the correctly calibrated mood. I let myself feel some existential hope.

As I guessed, it turned out not every country signed it. That being what it is, I still felt it is the case this is a monumental achievement, something that leads to the elimination of global thermonuclear war as a matter of when, not if. That the timeline to that world, of Global Zero or Global Very Small Defensive Stockpile, is definite and finite. That this treaty will gather momentum, and not decrease in efficacy over time. That the Sword of Damocles was a little less wobbly over our heads; perhaps it was on the order of a 1% reduction in x-risk, given it was a major chunk of reduction in nuclear risk, and nuclear risk is a major chunk in x-risk. That maybe, just maybe, people collectively can in fact be saner than I thought, and not get narrowmindedly stuck in brittle finite game framings of coordination problems. I did not actually expect a treaty banning nukes to exist, and it was a welcome surprise. I think we should let ourselves recognize when a major, major existential achievement has been unlocked, and not get stuck in perpetual cynicism about the state of the world. 

Luisa's article suggests otherwise. Reading it, I agree that formal impact seems very low. It's still another step in the right direction. I look forward to the article on informal means of impact.