What the nuclear ban treaty means for America's allies

What the nuclear ban treaty means for America's allies

This article appeared here in War on the Rocks and is written by Dr Heather Williams. Williams is a Stanton Nuclear Security Fellow at the MIT Security Studies Program. She is visiting from King’s College London, where she is a lecturer in the Centre for Security Studies and Defence Studies Department. Her research focuses on arms control and emerging technology, the global nuclear order, and social media and nuclear escalation.

November 5, 2020 | War on the Rocks | Heather Williams
Photo of protester for the International Campaign to Abolish Nuclear Weapons
Heather Williams
November 5, 2020
War on the Rocks

On Oct 24, 2020, Honduras ratified the Treaty on the Prohibition of Nuclear Weapons, also known as the “nuclear ban treaty,” becoming its 50th member. This sets in motion a 90-day countdown for the treaty’s entry into force. Notably, not a single state that possesses nuclear weapons has signed or ratified the treaty.

The nuclear ban treaty prohibits nearly all activities associated with nuclear weapons, such as possession, stockpiling, and testing. Additionally, members of the treaty cannot “assist, encourage or induce, in any way, anyone to engage in any activity prohibited to a State Party under this Treaty” or “seek or receive assistance in any way” from the activities prohibited by the treaty.

This means that states cannot have any direct involvement in practices that support the continued possession or “threat to use” nuclear weapons. This has clear implications for the United States and for NATO, a military alliance that falls under the US nuclear umbrella and continues to rely on nuclear deterrence.

Whether or not the treaty delivers on its disarmament promises or has a major impact on US or NATO nuclear postures ultimately depends on what its members and supporters do next and if it can prove that it is more than just a symbolic protest against the nuclear status quo.

For eight years, I have been researching and participating in events leading up to the ban treaty’s entry-into-force. I have written elsewhere why a nuclear ban treaty would be unethical and polarizing. This article is different. Now that the treaty is a reality, I will assess the pros and cons of it from the perspectives of America’s European allies. At present, membership is too great a risk for America’s allies until the treaty proves whether it improves or undermines members’ security and addresses concerns regarding its credibility.

What is the Logic of a Treaty Banning Nuclear Weapons? 

The Treaty on the Prohibition of Nuclear Weapons was concluded in July 2017 with the support of 122 countries. It opened for signatures a few months later. Members include historical leaders in nuclear disarmament efforts, such as Mexico, Ireland, and New Zealand, along with states that have suffered because of nuclear testing, such as Fiji and Samoa. Since then, it has accumulated signatures, with Honduran ratification marking the beginning of the treaty’s entry into force.

At least two major factors contributed to the evolution of the treaty. First, states are disappointed with the lack of progress towards nuclear disarmament within more traditional forums, such as the Nuclear Non-Proliferation Treaty and the Conference on Disarmament. In the lead-up to the treaty’s negotiation, over 100 states participated in a series of three conferences on the humanitarian impacts of nuclear weapons. These conferences included testimony from the hibakusha, survivors of the nuclear bombings of Hiroshima and Nagasaki, along with research on “nuclear winter” and risks of nuclear weapons use. For many participants, the humanitarian conferences were meant to reframe the moral acceptability of nuclear weapons as part of a process towards their ultimate elimination, similar to the process for banning anti-personnel land mines and cluster munitions.

Second, civil society lobbied hard for this treaty, particularly through the International Campaign to Abolish Nuclear Weapons, a consortium of non-governmental organizations, which won the Nobel Peace Prize in 2017. Civil society lobbied governments and launched campaigns such as Don’t Bank on the Bomb and the Cities Appeal, which has been signed by the mayors of Washington, D.C., and Paris, calling on their national governments to join the nuclear ban treaty. In her Nobel Peace Prize acceptance speech, Beatrice Fihn — the director of the International Campaign to Abolish Nuclear Weapons — appealed directly to America’s allies: “To the nations who believe they are sheltered under the umbrella of nuclear weapons, will you be complicit in your own destruction and the destruction of others in your name?” The expanding profile of the nuclear ban treaty is largely due to the work of civil societies, which have targeted US allies in their effort to bring the treaty into effect.

From the outset, the United States and other nuclear weapons possessors have been opposed to the idea of a nuclear weapons ban. In 2014, Under Secretary of State for Arms Control and International Security Rose Gottemoeller stated explicitly that “[t]he United States cannot and will not support” calls for the negotiation of a nuclear weapons ban treaty. The five nuclear-armed states recognized by the Nuclear Non-Proliferation Treaty have also consistently opposed the nuclear ban treaty and argued it cannot be a substitute for the Nuclear Non-Proliferation Treaty.

Critics argue that the nuclear ban treaty is not a viable tool for nuclear disarmament because it does not have a robust verification regime and because it might undermine existing disarmament and nonproliferation efforts, such as the Nuclear Non-Proliferation Treaty. An additional criticism is that the nuclear ban treaty will be unable to achieve its aim of establishing a new legal norm against nuclear weapons, similar to what exists for biological and chemical weapons, because it does not include a critical mass of states, including those that actually possess nuclear weapons. By focusing on the weapons rather than the security environment, it ignores the dynamics that drive states to rely on nuclear weapons in the first place.

So if the United States isn’t likely to join the nuclear ban treaty, why should American policymakers and experts care about its entry into force? In short, because NATO members are concerned with the issue of disarmament and might be tempted to join the treaty over time. This would have significant ramifications for the US nuclear mission and could potentially polarize NATO.

Can a NATO Member Join the Nuclear Ban Treaty?

The treaty’s supporters have consistently targeted America’s European allies to withdraw from NATO’s nuclear mission. Thus far, their efforts have failed: NATO remains steadfast in its commitment to nuclear deterrence, supported by the strategic nuclear arsenals of France, the United Kingdom, and the United States, as well as US nuclear weapons forward deployed in Europe.

However, from the perspective of America’s European allies, there could be some benefits to nuclear ban treaty membership. European governments are under pressure from a portion of the public that supports nuclear disarmament. Membership in the treaty would be a symbolic commitment to “general and complete disarmament,” as mandated in Article VI of the Nuclear Non-Proliferation Treaty. In a recent letter, 56 former leaders of NATO countries argued that the ban treaty can “help end decades of paralysis in disarmament.” Finally, allies would potentially claim some international moral leadership on humanitarian grounds by distancing themselves from the most destructive weapons on earth.

But treaty membership would come at a cost to national security. If a NATO ally were to join the nuclear ban treaty, this means they would have to renounce the threat to use nuclear weapons on their behalf — the “nuclear umbrella” — and cease to support NATO’s nuclear mission. More importantly, five NATO members directly support the US nuclear mission through the basing of dual-capable aircraft, which could constitute the possession, receiving, threatening to use, stationing, installation, or deploying nuclear weapons.

At present, membership in NATO and the nuclear ban treaty seem mutually exclusive. According to Brad Roberts, a nuclear policy expert at Lawrence Livermore National Laboratory, “At least three times over the last decade NATO heads of state or government have unanimously endorsed a continued role for nuclear weapons in the alliance’s deterrence and defense posture.” A recent NATO information sheet stated that the nuclear ban treaty “is inconsistent with the Alliance’s nuclear deterrence policy, and will not enhance any country’s security.” “As long as nuclear weapons exist,” went the most recent 2019 declaration, “NATO will remain a nuclear alliance.”

A united front is crucial: If a single NATO member were to join the treaty, it could have serious repercussions for the entire alliance. For example, were the Netherlands to join the nuclear ban treaty, it would be forced to end its direct support to NATO’s nuclear mission. That mission was declared “a crucial part of NATO deterrence and defence” by the Dutch government’s independent advisory council in 2019. Additionally, the Netherlands would likely have to refrain from participation in any nuclear-related exercises and signing any joint statements that threaten to use nuclear weapons. This would either leave the Netherlands as an outlier within NATO or force it to withdraw from the alliance altogether. Such a scenario would not only undermine Dutch security, but also European stability and the unity of NATO.

Many of the treaty’s advocates argue that NATO members can join the treaty with “only an incremental reduction of the salience of nuclear weapons in its security doctrine.” According to this line of argument, “threat to use” or possession does not necessarily equate to deterrence. Israel is an example of a state that practices deterrence, but without ever explicitly acknowledging possession of nuclear weapons or threatening to use them. Nuclear latency or ambiguity, therefore, might be possible without violating the nuclear ban treaty. While this might prompt a nuanced legal debate, pointing to a nuclear possessor like Israel as an exemplar for how NATO members might justify nuclear ban treaty membership is specious. Arguments that policies of deterrence do not constitute the “threat to use” nuclear weapons misrepresents deterrence, and suggests a lack of seriousness on the part of the treaty’s supporters to achieve their aim “to completely eliminate such weapons.”

Treaty advocates also argue that NATO members can join the nuclear ban treaty — however, NATO as an alliance would have to change in response. This would have implications for NATO’s nuclear posture, including a rejection of nuclear deterrence, and “in particular for hosting nuclear weapons on national territories and participating in nuclear planning.” In practice, it would be up to nuclear ban treaty members to ensure compliance with the treaty and NATO members to ensure their security. This seems highly unlikely given NATO’s consistent and united messaging on the role of nuclear weapons in European security. A major study by Sweden, a NATO partner, rejected membership on the grounds that it could damage the country’s security and relationship with NATO.

What is Next for the Nuclear Ban Treaty?

Whether or not a NATO member joins the nuclear ban treaty ultimately depends on whether or not the two memberships are compatible. Compatibility will have to be determined by both nuclear ban treaty and NATO members. But it also depends on whether treaty membership is worth the potential security risks of abandoning nuclear deterrence.

By joining the nuclear ban treaty, NATO members would be giving up extended nuclear deterrence, potentially jeopardizing the unity of one of the world’s most successful cooperative security organizations. States aren’t going to take such a major step unless they believe that the alternative is somehow more secure. The ban treaty needs to address at least four major questions to prove it is a credible and practical pathway towards nuclear disarmament.

First, how will the treaty address questions of compliance? In addition to numerous concerns raised about the treaty’s verification measures, two cases are worth mentioning here. Kazakhstan hosts a site at Sary-Shagan to test Russian reentry vehicles, which are capable of carrying nuclear weapons. This arguably counts as “assistance” towards development and possession of nuclear weapons, depending on the interpretation of nuclear ban treaty members, and would be in violation of the treaty. Similarly, Palau is a treaty member and part of the Compact of Free Association with the United States. According to the terms of the agreement:

[The] Government of the United States has the right to operate nuclear capable or nuclear propelled vessels and aircraft within the jurisdiction of Palau without either confirming or denying the presence or absence of such weapons within the jurisdiction of Palau.

Both of these cases should raise questions among ban treaty members regarding the compliance of all member states. How the treaty addresses them will be a test of its credibility and seriousness.

Second, will the treaty supporters target all nuclear possessors or continue to focus on Western democracies? Thus far, treaty supporters, particularly civil society organizations, have focused their attention on nuclear-armed democracies, such as France, the United Kingdom, and the United States, as well as other NATO members. While this is understandable from a campaigning perspective (civil society isn’t as active in Beijing or Pyongyang as it is in Washington), now that the treaty will enter into force, its members should focus on all nuclear weapons possessors, rather than those that are just more transparent.

Third, what is its relationship with the Nuclear Non-Proliferation Treaty? Members of the nuclear ban treaty state their full support for the Nuclear Non-Proliferation Treaty. The International Campaign to Abolish Nuclear Weapons does not want any states to withdraw from it. But some supporters have begun to suggest that states should consider abandoning the Nuclear Non-Proliferation Treaty for the ban treaty on the grounds that, “the NPT [Nuclear Non-Proliferation Treaty] became the cornerstone of a severely hypocritical nuclear order.” If members of the nuclear ban treaty remain committed to the Nuclear Non-Proliferation Treaty and want the two treaties to be separate, they can take concrete steps to make this a reality. The nuclear ban treaty could, for example, require all its members to also be members in good standing of the Nuclear Non-Proliferation Treaty, which is not in the current ban treaty text.

Finally, who will pay for the operation of the nuclear ban treaty? Article Nine of the treaty stipulates that members and observers are responsible for covering meeting, implementation, and verification costs. This includes costs incurred by the United Nations, such as circulating the treaty’s materials. For many countries, these are not insignificant costs. At present, 16 of the nuclear ban treaty’s 50 members are behind on their U.N. dues, and of the four countries that have lost voting rights in the United Nations due to payment arrears, one is a treaty member and two are signatories. These dues can range from tens of thousands to tens of millions of dollars, though nuclear ban treaty dues would likely be much lower. However, this is still a practical consideration in estimating the treaty’s effectiveness and will undoubtedly influence the longevity of the treaty and its ability to fulfill its mandate.


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.

While the treaty works through these issues, the United States cannot afford to ignore it. Rather, the United States should engage with allies, listen to their concerns about nuclear risks and disarmament, and pursue opportunities for cooperation on nuclear risk reduction. The Creating an Environment for Nuclear Disarmament initiative is one such opportunity under the leadership of the six co-chairs — the Netherlands, Morocco, South Korea, United States, Germany, and Finland. It should not treat deterrence and disarmament as mutually exclusive endeavors. Providing a strong extended deterrent to allies while also being sensitive to disarmament pressures is indeed a delicate balance, but it is one that the United States has to pursue with greater nuance.

Dr Heather Williams is a Stanton Nuclear Security Fellow at the MIT Security Studies Program. She is visiting from King’s College London, where she is a lecturer in the Centre for Security Studies and Defence Studies Department. Her research focuses on arms control and emerging technology, the global nuclear order, and social media and nuclear escalation.