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Commentary | 30 January 2025

The CTBT: A success story and keystone for reinforcing the NPT regime ahead of the next 2026 NPT Review Conference

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) was opened to state signatures 28 years ago and, to this date, has not yet entered into force. On account of this, it has often been deemed a failure; however, on many metrics, the Treaty has nonetheless achieved some notable successes.

The Treaty enjoys near-universal support, with 187 countries having signed and 178 having ratified it, demonstrating widespread global support for the object and purpose of the CTBT. The CTBT has also established a firm and unchallenged norm against nuclear testing. Only India, Pakistan and North Korea have conducted tests since it opened for signatures in 1996. In this century, only one State – North Korea – has breached the norm and tested nuclear weapons. Additionally, the International Monitoring System (IMS) – a key component of the CTBT’s unique verification regime – is fully operational, ensuring no nuclear test goes undetected. Beyond its primary role in detecting nuclear explosions, the IMS generates valuable data with broad civil and scientific applications, including tsunami warning systems and nuclear emergency response.

In light of this, it is clear that the CTBT represents a global public good that must not be taken for granted, especially amid today’s complex geopolitical landscape. We are witnessing rising global anxieties over nuclear threats, including the potential use of nuclear weapons, possible further nuclear tests, and risks of nuclear proliferation with increased stockpiles of enriched uranium. This complexity was further highlighted by the recent de-ratification of the CTBT by the Russian Federation in November 2023. Yet, there has also been renewed momentum toward universalising the CTBT, with nine new ratifications and one additional signature in the past two years, underscoring that countries continue to recognise the CTBT’s value.

It is clear that the CTBT represents a global public good that must not be taken for granted, especially amid today’s complex geopolitical landscape. Eleonora Neri

While the CTBT has already demonstrated significant success, its full potential can only be realised with its formal entry into force. The CTBT has not formally entered force due to a strict entry-into-force provision. According to Article 14 of the Treaty, 44 States with nuclear capabilities (Annex II States) must ratify the Treaty for it to enter into force. Currently, nine out of 44 States have yet to ratify the CTBT. Of these, six States (China, Egypt, Iran, Israel, the United States, and the Russian Federation) have signed but not ratified the Treaty, while three States (India, Pakistan, and North Korea) have not yet signed. Only when the Treaty enters into force will States be able to fully leverage all four components of its verification regime: consultation and clarification, confidence-building measures, IMS, and On-Site Inspections (OSI). Therefore, achieving its entry into force remains essential, now more so than ever.

Despite these challenges, the CTBT remains a cornerstone of the non-proliferation and disarmament architecture, with a vital and complementary role alongside the landmark Non-Proliferation Treaty (NPT). In fact, the call to ban nuclear testing predates the call for the NPT. The Partial Nuclear Test Ban Treaty (PTBT) of 1963 marked the first international legal constraint on nuclear weapons by restricting nuclear testing underground, serving as a stepping stone to the NPT.

The CTBT is closely intertwined with the NPT, as reflected in the preambles of both treaties: the NPT Preamble envisions the CTBT, while the CTBT Preamble references Article VI of the NPT, which focuses on nuclear disarmament. The CTBT has been a fundamental component of every forward-looking adopted output in the NPT review process.

The CTBT remains a cornerstone of the non-proliferation and disarmament architecture, with a vital and complementary role alongside the landmark Non-Proliferation Treaty (NPT) Eleonora Neri

At the 1995 NPT Review and Extension Conference, the commitment to conclude CTBT negotiations by 1996 was a crucial element of the decision to extend the NPT indefinitely.

At the 2000 NPT Review Conference, two of the 13 practical steps were directly connected to the CTBT. These 13 steps were unanimously adopted to advance the effective implementation of Article VI of the NPT, as well as paragraphs 3 and 4(c) of the 1995 NPT Review and Extension Conference’s second decision, titled “Principles and Objectives for Nuclear Non-Proliferation and Disarmament.”

Likewise, at the 2010 NPT Review Conference, as many as five action items in the NPT Action Plan were dedicated to the CTBT and nuclear testing. The Action Plan on Nuclear Disarmament outlines concrete steps for the total elimination of nuclear weapons. Actions 10, 11, 12, 13, and 14 directly support the CTBT’s objectives.

The CTBT plays a crucial role in advancing the NPT’s first two pillars of the NPT: non-proliferation (Pillar I) and disarmament (Pillar II). Nuclear testing plays a crucial role in advancing nuclear weapons capabilities. By prohibiting such tests, the CTBT effectively limits nuclear weapons proliferation, whether it involves new countries acquiring nuclear arms, existing nuclear states upgrading their arsenals, or the development of advanced nuclear weapon technologies—thus supporting non-proliferation both vertically and horizontally. The CTBT is essential to nuclear disarmament as it fosters confidence that any nuclear test would be detected.

Additionally, the IMS serves as a mechanism for engaging both NPT States Parties and Non-NPT States in constructive dialogue on disarmament issues. For example, Israel—a Non-Party to the NPT—is a Signatory State to the CTBT and hosts three certified IMS facilities. Similarly, despite announcing its de-ratification of the CTBT, the Russian Federation also declared the completion of its 32nd and final IMS station within its territory soon after. Notably, Russia has remained a signatory to the Treaty and has expressed its intent to uphold the nuclear testing moratorium unless the US tests first while continuing to operate IMS stations on its territory. Particularly during a time of heightened concern over the potential resumption of nuclear testing, the IMS plays a necessary role in encouraging other Annex II States, like China and the United States, to remain actively engaged in efforts to enhance monitoring and detection of potential nuclear test activity in the region.

In sum, the CTBT stands as a fundamental multilateral measure—non-discriminatory, inclusive, verifiable, and effective—advancing the goal of a nuclear weapons-free world. Eleonora Neri

In sum, the CTBT stands as a fundamental multilateral measure—non-discriminatory, inclusive, verifiable, and effective—advancing the goal of a nuclear weapons-free world. As we approach the 2026 NPT Review Conference, it is essential to elevate the CTBT’s profile to support and reinforce the NPT regime. Below are some personal recommendations for all CTBT Signatory States to consider in pursuit of this goal:

Advancing universalisation of the CTBT
  • The upcoming 30th anniversary of the CTBT in 2026 presents an important opportunity to promote a positive narrative about the Treaty and emphasise the critical importance of its entry into force.
  • States should actively highlight the CTBT’s achievements and its role in strengthening international security at relevant forums such as the Conference on Disarmament or by organising dedicated events to mark this milestone.
  • Efforts by Signatory States should be intensified to engage with States that have not yet signed or ratified the CTBT. Signatory States should actively seek opportunities to foster diplomatic dialogue and implement targeted outreach initiatives, either independently or in conjunction with major international or regional meetings, to encourage non-signatory states to take concrete steps toward formalising their commitment to the Treaty.
  • Signatory States should take ownership of the Treaty and act as its champions, recognising that achieving the CTBT’s entry into force and universality is not solely the responsibility of the CTBTO but a shared obligation that rests with them as well.
  • Signatory States should actively promote supportive and constructive language related to the CTBT at meetings of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO) and across relevant forums, including the NPT Review Conferences and Preparatory Committees.
  • Signatory States should lead efforts to raise awareness about the CTBTO Youth Group to inspire the next generation within their respective countries to actively join efforts and contribute to the global call for a nuclear test ban. This includes promoting the Group’s initiatives in schools or universities, as well as creating opportunities for collaboration and meaningful youth participation in the work of the CTBTO. Signatory States can also play a key role by providing funding to support and expand these efforts.
Reinforcing the global norm against nuclear testing
  • Signatory States should continue to highlight during NPT Review Conferences and Preparatory Committees that the prohibition of nuclear testing is an integral part of achieving the goals of the NPT, underscoring its role in advancing non-proliferation and disarmament efforts. Ideally, this should continue to be reflected in the outcome documents.
  • Signatory States should encourage Annex II States to publicly reaffirm their commitment to maintaining the nuclear testing moratorium, demonstrating their dedication to global security and the objectives of the CTBT.
  • Signatory States should reaffirm CTBT language from past NPT Review Conference documents and update it to reflect current global security needs in drafting NPT final documents. In particular, reference to Action 11 of the 2010 NPT Review Conference, which urges States to refrain from any actions that would undermine the object and purpose of the Treaty until the CTBT enters into force.
Enhancing support for the CTBTO and completing the Verification System
  • Signatory States should actively engage with the CTBTO to promote the installation and complete certification of IMS facilities within their territory. They should also ensure that Facility Agreements are signed if they are not already in place.
  • Signatory States are urged to pay their assessed contributions to the CTBTO on time and in full, as this demonstrates political commitment and supports the activities of the CTBTO.
  • Signatory States should make efforts to promote the use of CTBTO data for scientific research and civil applications within their respective countries, including the signing of Tsunami Warning Agreements.
  • Signatory States should support the participation of more scientific experts in CTBTO capacity-building and training programs, as well as host CTBTO regional workshops to expand technical expertise.

The CTBT has proved to be a success story even prior to its entry into force, already making a profound positive impact while reinforcing the NPT’s goals by curbing nuclear testing and promoting global security. With stronger support from Signatory States, it could unlock even greater potential, paving the way for a more robust non-proliferation and disarmament regime and a safer world.

The European Leadership Network itself as an institution holds no formal policy positions. The opinions articulated above represent the views of the authors rather than the European Leadership Network or its members. The ELN aims to encourage debates that will help develop Europe’s capacity to address the pressing foreign, defence, and security policy challenges of our time, to further its charitable purposes.

Image credit: Wikimedia Commons / National Oceanic and Atmosphere Adminstration