Legal Reflections on the Irreversibility of Nuclear Disarmament

ABSTRACT

While the shared objective of a nuclear-weapon-free world has always implied an element of irreversibility, the term as such has not been consistently used in important disarmament texts before. This article provides legal reflections on the topic of irreversibility of nuclear disarmament. It intends to demonstrate how current treaty-based instruments, evolving prohibition norms, and safeguards can contribute to higher levels of irreversibility. The possibility of a withdrawal, even when a strong clause makes it difficult under a certain treaty, as well as the danger of a violation of a treaty, remain a major challenge to irreversibility. Only strong sanctions by the international community can make such a behaviour as costly and unattractive as possible, thereby minimizing the probability.

KEYWORDS:

• Irreversibility
• nuclear disarmament
• CTBT
• TPNW

While the shared objective of a nuclear-weapon-free world has always implied an element of irreversibility, the term as such has not been consistently used in important disarmament texts before. Explicit references within the context of the Non-Proliferation Treaty (NPT) Review Process are the most prominent, but other treaties also engage with the concept even if implicitly. Step 5 of the 13 practical steps of the Final Document of the 2000 NPT Review Conference states that the “principle” of irreversibility is “to apply to nuclear disarmament, nuclear and other related arms control and reduction measures”.

The concept of irreversibility enjoys broad support and can be found again in the Final Document of the 2010 Review Conference. There it is linked to transparency and verification, which constitute important principles for nuclear disarmament in their own right, but irreversibility can also be regarded as a separate principle means. Stressing the close connection of the three principles has resulted in making irreversibility an often neglected corollary of verification and transparency. Indeed, in bilateral, plurilateral and multilateral settings the process leading to irreversibility will need transparency and verification. But making nuclear disarmament irreversible is possible even without full transparency and being verified by other states or international organisations. Nuclear weapon programmes have been given up by a number of states unilaterally and the case of South Africa proves that a nuclear weapon state can decide and implement the elimination of its nuclear weapons on its own with verification measures only ex post. These facts corroborate that irreversibility merits to be considered not only in tandem with verification and transparency.

There is no generally accepted definition for irreversibility in the nuclear disarmament context. Nor is such a definition necessary in a multilateral diplomatic context. What is needed is rather a broad vision that is shared. As a simple personal working definition for the disarmament context, I would suggest that irreversible means seeking to exclude re-armament after disarmament steps or comprehensive disarmament have been accomplished, in particular the re-constitution of a nuclear weapons programme.¹ It is about erecting strong barriers against backsliding from meeting disarmament commitments related to nuclear weapons.

Irreversibility is not an absolute status, which can be achieved once and for all times, but a constant striving over a long period without an end date in order to make the option of re-armament as difficult and costly as possible. Irreversibility is thus rather a continuum than a feature attained at a certain point in time. As Cliff, Elbahtimy and Persbo have argued in their study, “Irreversibility in Nuclear Disarmament: Practical steps against nuclear rearmament” (Cliff, Elbahtimy, and Persbo 2011), “irreversibility in the context of nuclear disarmament should be defined in terms of the costs and difficulty of reversal. Irreversibility thus becomes a scale – not the binary state implied by dictionary definitions of the term – with readily reversible actions at the low end and measures that are highly difficult and costly to reverse at the other.”

In such a context, the factors that incentivize and sustain irreversible disarmament include political, societal, legal, military, and technical factors (Anthony 2011). Their interplay is crucial, and they do not have to follow a pre-established sequencing. Rather, these factors should be simultaneously at work. They are interconnected, interdependent and mutually re-enforcing.

The technical requirements go beyond the elimination of all nuclear warheads and a cut-off of fissile material production. It also encompasses the destruction of the industrial infrastructure of the nuclear weapons industry as well as the downblending of enriched uranium and the disposal of plutonium formerly used for military purposes. However, it is likely that taking apart of nuclear warheads would be undertaken in the same plants where they were assembled and the dual-use character of certain nuclear activities as well as the impact on environment have to be considered. The start of the technical process towards irreversible nuclear disarmament will depend on a political reappraisal of the threat associated with nuclear weapons and their role for achieving security. This is just to showcase the challenges and long-term character of the technical aspects of an irreversibility process.

On a bilateral, plurilateral or multilateral path towards the elimination of nuclear weapons commitments will play a major role. The most binding form of a commitment is a legal commitment. “A legal commitment can serve to reinforce and further legitimize a political commitment” (Spillman 2023). The following sections will demonstrate how current treaty-based instruments, evolving prohibition norms, safeguards and withdrawal clauses can contribute to higher levels of irreversibility.

Nuclear disarmament steps have been treaty based in most instances with the notable exception of South Africa, the only case of complete nuclear disarmament so far. Bilateral, plurilateral and multilateral treaties could pave the path towards a world without nuclear weapons. While the NPT is regarded the cornerstone of nuclear disarmament, it does not deal with the question of how to make nuclear disarmament irreversible. On purpose and reflecting a lack of consensus on certain pertaining issues at the time of the negotiations that ended in 1968, many relevant issues were left out to be regulated by later legal instruments. Since then, this short legal text has been complemented by more specific legal instruments supporting its implementation in all three pillars.

The Comprehensive Test Ban Treaty (CTBT) is such a legal instrument for the purpose of irreversibility. Banning nuclear weapons test explosions and any other nuclear explosions, the object of this treaty, makes the re-constitution of a nuclear weapons programme more challenging. During the treaty negotiations, the mistrust among nuclear weapon states had resulted in an innovative entry-into-force clause that made it dependent on the ratification of certain named countries. Although the CTBT has been ratified by 177 states since its adoption by the UN General Assembly in 1996, it could not enter into force so far because of the outstanding ratification by nuclear weapon states like China and the United States. In November 2023, the Russian Federation took the unusual step to de-ratify the treaty in order to go back to the same status as the United States, which is only a signatory. Signatory States are generally obligated by international law to refrain from acts that would defeat the object and purpose of a treaty (unless they have made their intention clear not to become a party to the treaty). In any event, it is likely that conducting nuclear testing is now a violation of customary international law. So they are under the legal obligation not to conduct nuclear weapons test explosions. France and the United Kingdom have ratified the CTBT. The three countries which have conducted nuclear weapons test explosions since 1996, the DPRK, India and Pakistan, have not signed the CTBT like Israel and are therefore not bound by its norms.

It can be argued that the effectiveness of the CTBT for the purpose of irreversibility has been eroded by scientific progress. Computer and sub-critical testing have made nuclear weapons test explosions as understood in the interpretation of the CTBT superfluous for the technologically most advanced nations. The CTBT adoption has initiated the establishment of a very comprehensive International Monitoring System of the Preparatory Commission of the Comprehensive Test Ban Treaty Organisation (CTBTO) consisting of 321 monitoring stations around the globe using four complementary scientific methods to detect a nuclear explosion. This international network has been almost completed and is fully operational. Its accuracy even allows the detection of tsunamis and groups of whales in the sea.

However, the key legal instrument for irreversibility is a norm that prohibits the possession, development and production of nuclear weapons. Even when the international community would have reached their declared goal of a nuclear-weapon-free world, the knowledge needed to rebuild nuclear weapons will never be forgotten. Therefore, such a legal prohibition norm is indispensable for maintaining a world without nuclear weapons.

This key legal instrument for the elimination of nuclear weapons and irreversibility has been negotiated in 2017 and has been adopted as the Treaty on the Prohibition of Nuclear Weapons (TPNW). Since its entry into force in 2021, more states are joining the TPNW. At the end of October 2023, 93 signatures, 69 ratifications and 4 accessions have been registered by the UN Legal Office.

Its Article 1 (a) prohibits to “develop, test, produce, manufacture, otherwise acquire, possess or stockpile nuclear weapons or other nuclear explosive devices”. This article embodies the main obligations for making nuclear disarmament irreversible.

Irreversibility requires legal norms under national law to implement those key prohibitions on a national level.

Art. 5 of the TPNW is dealing with national implementation:

“1. Each State Party shall adopt the necessary measures to implement its obligations under this Treaty.

2. Each State Party shall take appropriate legal, administrative and other measures, including the imposition of penal sanctions, to prevent and suppress any activity prohibited to a State Party under this Treaty undertaken by persons or on territory under its jurisdiction or control”.

In the penal codes of a number of countries, the participation in the development, production and manufacture or transfer of nuclear weapons is prohibited. As an example, § 177a of the Austrian Penal Code may be mentioned. It foresees 1 to 10-year imprisonment for such actions.

The fact that until now no nuclear possessor state has joined the TPNW does not diminish the importance of its prohibitions for the purpose of irreversibility. As long as some states want to cling to their nuclear weapons arsenals, they will not sign up to such prohibition norms. In order to eliminate nuclear weapons, a political and societal change of mind will be needed. The TPNW offers two avenues for nuclear possessor states to join the treaty in its Article 4, basically sign and start destruction or destroy your arsenal first and join thereafter.

Only once nuclear disarmament steps have been taken, irreversibility measures will become operational. But the establishment of the legal norm prior to the establishment of a world free of nuclear weapons serves to bring about the preconditions and goalposts of such a world and its maintenance.

The history of the conventions leading to the elimination of a particular weapon, not least the other classes of weapons of mass destruction – biological and chemical weapons, has shown that a legal prohibition norm already has to be in place in order to start the elimination process. The Chemical Weapons Convention, which entered into force in 1997 is a good example. It started the process of the destruction of the chemical weapons stockpiles that has been completed only in 2023. With regard to nuclear weapons, such a legal prohibition norm is not contained in the NPT, yet the full implementation of its nuclear disarmament obligation in Article VI requires it. Like the CTBT, the TPNW is complementing and supporting the NPT.

Although safeguards are first and foremost a verification tool, they will make an important contribution to instilling trust in the non-existence of a nuclear weapons programme. Under Art. III of the NPT, each non-nuclear-weapon state undertakes to accept safeguards for the verification of the fulfilment of its obligations under the Treaty. With the destruction of their last nuclear weapons, present nuclear weapon possessor states will become non-nuclear weapon states and thus be subject to the obligation to conclude safeguards agreements with the IAEA, as far as they are states parties to the NPT.

At present, nuclear weapons activities and fissile material for military purposes of nuclear weapon states are not inspected by the IAEA. Since about 80% of all fissile material is held in military stocks and even a fissile material cut-off treaty would not touch the vast existing military fissile material quantities, full safeguard inspections in former nuclear weapon possessor states would constitute a major breakthrough.

The maintenance and, in the case of no safeguards agreement, the conclusion of safeguards agreements with the IAEA is also an obligation under the TPNW in its Art. 3. And Art. 4 of the TPNW regulates the case of safeguards of nuclear possessor states that have joined the TPNW, but not yet completed the destruction of their nuclear weapons for the transition period: Such a State Party shall conclude a safeguards agreement with the IAEA sufficient to provide credible assurance of the non-diversion of declared nuclear material from peaceful nuclear activities and of the absence of undeclared nuclear material of activities in that State Party as a whole.

With the exception of unilateral disarmament, the destruction of the nuclear arsenal and of the nuclear weapons industry will most likely come about through bilateral, plurilateral and multilateral treaties.

So far, all such treaties have withdrawal clauses. How easy or difficult it is to withdraw from a treaty will play a major role in judging the degree of irreversibility. The highest degree of irreversibility would be offered by a treaty that explicitly prohibits a withdrawal. Legally, this would be possible, but politically it could keep away countries that have a tradition of politically or even legally interdicting the government to enter into obligations that cannot be rescinded, or countries that are particularly reluctant to accept such a far-reaching obligation. During the negotiations of the TPNW, Chile, with the support of a number of states, made an attempt to include such a no-withdrawal clause, but its proposal was not acceptable to other states.

Most relevant disarmament treaties entered into force so far provide for a possibility of withdrawal for any state party, if it decides that “extraordinary events related to the subject matter of the treaty have jeopardized the supreme interests of the country”. Those extraordinary events are not further explained and therefore leave a lot of room for interpretation for determining what could be subsumed under these words. Although this judgement is up to the withdrawing state party in exercising its sovereignty, it would have to be done in accordance with the fundamental treaty law principle of good faith (Casey-Maslen 2019). As the withdrawal of the DPRK from the NPT has shown, it can be expected that a withdrawal will be contested, but that does not bring back the former state party which has left.

The TPNW contains the following solution for a strong withdrawal clause:

“Art. 17: Duration and Withdrawal

1. This treaty shall be of unlimited duration.

2. Each State Party shall, in exercising its national sovereignty, have the right to withdraw from this Treaty if it decides that extraordinary events related to the subject matter of the Treaty have jeopardized the supreme interests of the country. It shall give notice of such withdrawal to the Depositary. Such notice shall include a statement of the extraordinary events that it regards as having jeopardized its supreme interests.

3. Such withdrawal shall only take effect 12 months after the date of the receipt of the notification of withdrawal by the Depositary. If, however, on the expiry of that 12-month period, the withdrawing State Party is a party to an armed conflict, the State Party shall continue to be bound by the obligations of the Treaty and of any additional protocols until it is no longer party to an armed conflict”.

This withdrawal clause makes withdrawal more difficult than Article X of the NPT which is essentially identical with Article 17 (2) of the TPNW. But the NPT foresees a time span of only 3 months until the withdrawal takes effect. Unlike the withdrawal under the NPT, the TPNW explicitly forbids the withdrawal taking effect during an armed conflict. This clause stems from international humanitarian law and creates an additional hurdle for withdrawal.

The possibility of a withdrawal, even when a strong clause makes it difficult under a certain treaty, as well as the always remaining danger of a violation of a treaty remains a major challenge to irreversibility. Only strong sanctions by the international community can make such a behaviour as costly and unattractive as possible, thereby minimizing the probability.

For the legal requirements of irreversibility of nuclear disarmament, the thesis of Cliff, Elbahtimy and Persbo is valid: “Irreversibility in the context of nuclear disarmament should be defined in terms of the costs and difficulty of reversal” (Cliff, Elbahtimy, and Persbo 2011).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Thomas Hajnoczi

Thomas Hajnoczi is a member of the European Leadership Network’s Senior Network. He held the post of Director for Disarmament, Arms Control and Non-Proliferation twice in his career in the Austrian Foreign Ministry. His last post abroad was Permanent Representative to the United Nations Office at Geneva (including the CD). He was closely involved in bringing about the Anti-Personnel Mine Ban Convention, the Treaty on the Prohibition of Nuclear Weapons and the EWIPA Political Declaration. He is pursuing his engagement for human security and disarmament by advising think tanks and NGOs.

Notes

¹ The focus on re-constitution is in line with the definition provided by Elbahtimy in this Special Issue (Elbahtimy 2023).