Can the TPNW Serve Ukraine?

Can the TPNW Serve Ukraine?

[Tobias Vestner is Head of the Research and Policy Advice Department at the Geneva Centre for Security Policy (GCSP), Fellow at Supreme Headquarters Allied Powers Europe (SHAPE), Non-Resident Fellow at the United Nations Institute for Disarmament Research (UNIDIR), and Honorary Senior Research Fellow at the University of Exeter. Juliette François-Blouin is a Programme Officer with the Security and Law Programme at the Geneva Centre for Security Policy (GCSP).]

Ukraine faces the threat of a nuclear attack. Shortly after having invaded Ukraine, President of Russia Vladimir Putin warned that the use of nuclear weapons was an option should anyone get in his way. Hence the question arises of whether yet unexplored international instruments could prove useful for Ukraine to protect itself against this existing nuclear threat. Specifically, could acceding to the Treaty on the Prohibition of Nuclear Weapons (TPNW) offer any additional protection or benefits to Ukraine? 

In a nutshell, accession to the TPNW would allow Ukraine to signal that it wants nothing to do with nuclear weapons and that it is doing everything in its power to live up to this commitment. Thereby, Ukraine can underline that any potential use of nuclear weapons by Russia would be grossly inappropriate and unjustified as well as assure Russia that it will not benefit from nuclear weapons or deterrence. In addition, by acceding to the TPNW, Ukraine can count on the network of TPNW states parties for political support against a nuclear attack and assistance in case of a nuclear strike. 

The Context

With the fall of the Soviet Union, Ukraine inherited the third-largest nuclear arsenal in the world. Under strong pressure from Russia and the United States, the country transferred all weapons back to Russia and acceded to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) as a non-nuclear State in 1994. Russia, the United States, and the U.K. signed the Budapest Memorandum which guaranteed the sovereignty, territorial integrity, and freedom from economic and political pressure of Ukraine. Similar declarations were issued independently by France and China.

Fast forward to Feb. 24, 2022, Russia attacked Ukraine. Three days later, Russia put its nuclear weapons forces on high alert. Kremlin spokesman Dmitry Peskov’s refusal to assert that Russia would not use nuclear weapons in Ukraine led analysts to conclude that “the chances of a conflict escalating into a nuclear war are greater than they have been for more than half a century”, to some maybe even greater than during the Cuban missile crisis

Among the potential scenarios, the most likely is the use of tactical nuclear weapons to break stalemate or avoid defeat. This would be in line with Russia’s escalate to de-escalate doctrine where a limited nuclear strike – or the threat thereof – inflicting tailored damage could be used as a strategic tool for de-escalation to force the opponent to retreat or revert to the status quo. This concern is shared by William J. Burns, Director of the CIA, although there is no intelligence on an imminent move. This would lead to a disaster, however. In this vein, the ICRC has warned after the outbreak of the war that nuclear weapons should not be used due to their disastrous humanitarian consequences.

Given Ukraine’s exposure to a potential nuclear attack, it makes sense to debate the merits of Ukraine’s decision to give up its nuclear arsenal. John Mearsheimer had indeed advocated in favor of Ukraine keeping the former Soviet nuclear weapons to ensure its security. Commentators posit, however, that such a move would have created endemic instability, and been politically and economically unbearable. The real issue would rather lie in the West’s inaction and failure to uphold its obligations under the Budapest Memorandum since the invasion of Crimea in 2014. Concerning Ukraine’s and its supporters’ options today, it has been argued that NATO should communicate to Russia that the use of nuclear weapons would prompt severe diplomatic, economic, and military consequences. 

Considering how Ukraine has used legal mechanisms and instruments for defending itself, it is worth asking if the TPNW is a further instrument that can serve Ukraine. Specifically, would acceding to the TPNW serve Ukraine? 

The TPNW as a Tool to Signal

The TPNW comprehensively prohibits nuclear weapons. It was negotiated in 2017 and entered into force in 2021 intending to foster the ‘nuclear taboo’, namely the internationally shared belief that nuclear weapons should not be used. Currently, there is no conclusive evidence that the norm against nuclear weapons has broadly been internalized by the international community so far. While there are indications that a significant part of the population of Western countries, including those of nuclear weapon states, consider the possible use of nuclear weapons as unacceptable, government policies still rely on nuclear deterrence. The permanent members of the UN Security Council (P5) and others also openly oppose the TPNW. With President Putin’s threats, it has become clear that he, his entourage, and the Russian military establishment have not internalized such a norm which would prevent them from even considering the use of nuclear weapons. 

However, as will be developed in a forthcoming article in the Washington International Law Journal, the TPNW’s function may not be so much about norm diffusion but to signal messages to states that remain outside of the treaty regime. Christopher A. Ford, former U.S. Assistant Secretary at the Bureau of International Security and Nonproliferation, had hinted at such a signaling function when criticizing the TPNW. In short, this means that the TPNW allows its states parties to communicate their views on nuclear weapons. More specifically, the TPNW’s messages are that nuclear weapons are illegal, immoral, and dangerous and that nuclear disarmament should advance. Fundamentally, the TPNW effectively signals that its state parties do not want anything to do with nuclear weapons. 

The TPNW as an Instrument for Ukraine

Building on the TPNW’s signaling function, Ukraine could accede to the TPNW to support its case against a nuclear attack targeting its state and people. Ukraine had not participated in the negotiations of the treaty, did not take part in the vote on its adoption, and has not signed the TPNW so far. Yet acceding to the TPNW now could serve Ukraine for several reasons.

First and foremost, by acceding to the TPNW, Ukraine could signal alongside other TPNW states parties to Russia and other states that it does not want anything to do with nuclear weapons. This would allow Ukraine to underline that it is a peaceful and non-threatening state that is opposed to any nuclear war. Thereby, it would highlight that any use of nuclear weapons against it would be grossly unjustified. Indeed, acceding to the TPNW would reinforce the message that Ukraine already sent when it relinquished its nuclear arsenal, namely that it distances itself from nuclear weapons. Since the fall of the Soviet Union, Ukraine has consistently chosen the path of denuclearization and de-escalation, preferring to ensure its security through international instruments as opposed to participating in nuclear deterrence. This reduced risks and eased tensions in the region as well as contributed to regional and global stability.

Becoming a party to the TPNW would involve legal obligations that would strengthen Ukraine’s stance against nuclear weapons. According to Articles 1(a) and 1(d) of the TPNW, states parties commit not to use nor “develop, test, produce, manufacture, otherwise acquire, possess or stockpile” nuclear weapons. Although Ukraine has already committed itself to not acquiring nuclear weapons under the NPT, these legal commitments would provide further assurances that Ukraine will not try to acquire nuclear weapons to defend itself against Russia. This would re-emphasize existing legal commitments and show that Ukraine is expending extra effort for living up to the most stringent legal standards. 

More importantly, according to Article 1(g) of the TPNW, State parties are prohibited to allow the “stationing, installation or deployment of any nuclear weapons or other nuclear explosive devices in its territory”. If Ukraine accedes to the treaty, this obligation would commit it to not benefit from extended deterrence or nuclear sharing that could be offered by the United States and NATO. This is crucial as Russia fears that Ukraine may become part of their nuclear umbrella. Ukraine can thus reassure Russia and other states that it will not do so. This could also represent an element of any potential neutrality policy of Ukraine. 

Consequently, the TPNW could serve as a political tool to delegitimize any use of nuclear weapons against Ukraine by enabling the country to reiterate its commitment to not possess or otherwise benefit from nuclear weapons, a commitment made even more believable by the incurring of legal obligations. It would constitute proof that the country adhered and committed to all the international instruments available. This would allow it to counter any potential accusations and fears by Russia that Ukraine would try to benefit from nuclear weapons. Moreover, this would clearly show that any attack would be grossly unjustified because Ukraine did all in its power to keep nuclear weapons out of the war and away from future confrontation. While a Russian nuclear attack against Ukraine would also be illegitimate absent Ukrainian accession to the TPNW, the accession would arguably increase the wrong and bring this to the international community’s attention.

Yet the benefits of accession to the TPNW could also go beyond signaling positions and intentions. Joining the TPNW would provide Ukraine with allies against the use of nuclear weapons. This has a political feature. Membership to the TPNW could mobilize political support by a community of like-minded states and non-governmental organizations who could defend Ukraine’s positions and needs for countering the nuclear threat both in international fora as well as bilaterally, including dialogue with Russia. The group of TPNW states parties could indeed become advocates for Ukraine specifically dedicated to the issue of reducing the nuclear threat. TPNW states parties are likely to invest their political weight and collaboration to aid Ukraine, first because nuclear attacks contravene their fundamental beliefs, and second because an attack on a TPNW state party could symbolically be viewed as an attack on the TPNW and its principles itself.

There is also a practical feature that would arise from joining the TPNW regime. In the event of a nuclear attack, TPNW states parties would be bound under Articles 7(3) and 7(4) to provide technical, material, and financial assistance to Ukraine and its victims. Any state and organization can assist the victims in the event of a nuclear attack. Yet states parties are legally bound to do so, which increases the probability for support. In addition, any respective mechanism can serve as a focal point for organizing such support. The group of TPNW states parties and associated non-governmental organizations could also prove useful partners to bring cases before international judicial mechanisms and develop legal arguments against the threat of use of nuclear weapons and/or the actual use of nuclear weapons. Related discussions and work for supporting Ukraine could already start at the first Meeting of states parties which will be held from 21 to 23 June 2022 in Vienna.


The added value of TPNW accession for Ukraine lies in its ability to signal Ukraine’s commitment to not benefit from nuclear weapons. This could impact the potential for nuclear escalation by delegitimizing a nuclear attack on Ukrainian soil and providing Ukraine with increased support via a network of states, thereby eventually lessening the nuclear threat. This may also be beneficial in the aftermath of the war as a means for assuring Russia as well as for contributing to regional stability. 

For Ukraine to benefit from the TPNW, however, it is crucial that states which traditionally oppose the TPNW, such as the United States, accept that the treaty can be used in this manner as well as support Ukraine’s potential steps in this direction. Regardless of the origin, rationale, dynamics, and challenges of the TPNW, this is a legal instrument that can serve Ukraine and hopefully contribute to European stability and security.

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