Thirty years after the Comprehensive Nuclear-Test-Ban Treaty (CTBT) opened for signature, its significance should hardly need explaining. The treaty has established a global norm around the prohibition of nuclear explosive testing and created an unparalleled international architecture to detect clandestine nuclear weapon tests. 

However, at 30, the CTBT faces considerable uncertainty and the global norm against testing can no longer be taken for granted. In October 2025, US President Trump called for the US to resume nuclear testing “on an equal basis” and ordered preparations for new tests. While most experts assumed that any resumption would take the form of a low-yield underground test, US officials, when asked, declined to rule out above-ground testing. The US administration has also publicly alleged that China conducted a clandestine nuclear test in 2020. At the 2026 Treaty on the Non-Proliferation of Nuclear Weapons (NPT) Review Conference, states supportive of the CTBT fought to retain a joint reaffirmation of the treaty’s significance in the draft outcome document against US objections. 

In responding to these developments, states and experts have emphasised that new nuclear tests would almost certainly be detected, not least thanks to the CTBT’s comprehensive verification regime; that for the US or Russia, resuming testing would make little sense, on neither technical nor strategic grounds; that a decision by any nuclear weapons state to resume testing would trigger others to follow, which would undermine global security; and that a weakened CTBT would damage the wider non-proliferation and disarmament architecture. 

These arguments are crucial. But the 30th anniversary also offers an opportunity to underline a more fundamental question: why should nuclear testing remain unacceptable in the first place? 

What nuclear explosions do to the places where they are conducted and to the people living “downwind” is rarely mentioned in global conversations about how to protect the CTBT. Yet these consequences were central to political demands for establishing a global ban on nuclear testing from the very beginning and are closely linked to the treaty’s core rationale, set out in its preamble: that ending nuclear explosions constrains qualitative arms racing and the spread of nuclear weapons. The CTBT’s 30th anniversary should therefore be seized as an opportunity to reconnect its technical capabilities with the broader reasons why nuclear testing became unacceptable. 

The CTBT’s extraordinary, technical success 

Thirty years after the treaty opened for signature, the CTBT has achieved remarkable things – despite never entering into force. With 187 signatures, it has one of the widest memberships of any international arms control agreement and has helped establish a global norm against nuclear testing that very few states openly challenge. The provisional architecture built around the CTBT has established a global monitoring system that is functional and, in many respects, more capable than envisaged during the negotiations. The International Monitoring System (IMS), which spans the entire globe, has made it extraordinarily difficult to conduct a nuclear explosion without being detected. 

The treaty’s main structural problem remains its failure to enter into force: this would require ratification by all so-called “Annex 2” states. Nine have yet to do so, including the US and China, as well as Russia since it revoked its ratification in 2023. The stalled ratification process, together with the recent allegations of clandestine testing, has made the effectiveness of the CTBT’s provisional monitoring and verification architecture all the more important – which has been pushed to the centre of how the treaty is defended. 

While the verification regime is a powerful demonstration of the CTBT’s effectiveness, it is only one part of the case for sustaining the global norm against testing. For the CTBT to build new political momentum, what the verification regime is able to achieve needs to remain connected to why it matters: the treaty’s contribution to disarmament and non-proliferation, but also the humanitarian and environmental consequences that the global test-ban prevents. 

Not an afterthought: the human costs of testing 

While the CTBT’s contribution to disarmament and non-proliferation figures prominently in diplomatic and political discussions on the CTBT, the human costs of nuclear weapons tests have been sidelined to a certain extent. 

Yet concerns about the humanitarian, health, and environmental consequences of not only atmospheric but also underground testing have always been at the forefront of global campaigns against nuclear explosions. The movement for a test-ban did not emerge solely from considerations of verification or from calculations about the benefits of a test-ban for non-proliferation. It also emerged from the lived experience of nuclear explosions and their consequences: radioactive contamination, damage to ecosystems, and effects on communities and future generations.  

The CTBT sits within a much longer history in which the physical, psychological, and cultural consequences of testing generated political demands for restraint by the nuclear powers. The negotiation of the 1963 Partial Nuclear-Test-Ban Treaty was strongly linked to public alarm at heightened levels of strontium-90 in children’s teeth. The Semipalatinsk test site closed in 1991 after a mass movement in Kazakhstan mobilised against the far-reaching humanitarian and environmental harm caused by Soviet nuclear testing. The CTBT does not ignore this history: its preamble explicitly refers to the environmental consequences of nuclear testing. 

The human costs of nuclear testing were therefore not an afterthought added to a technical arms control project. They were part of the political history through which nuclear testing came to be regarded as unacceptable in the first place. 

The experiences of affected communities remain politically powerful, not merely historically significant. In the US, the continuing debate over compensation for the consequences of testing has attracted broad bipartisan support, while opposition to renewed testing has been articulated by Nevada officials and affected communities alike. In France and the United Kingdom too, affected communities, veterans, and political representatives across party lines regularly raise questions of compensation, reparations, and opposition to renewed testing.  

Highlighting humanitarian and environmental legacies of nuclear testing should not be seen as an alternative to pointing out the undeniable benefits of the CTBT and its significance for global disarmament and non-proliferation. They are part of the same history that resulted in the negotiations of the CTBT, provide the existing defence of the treaty greater resonance, and create renewed political momentum towards protecting the test-ban regime. 

A stronger defence 

Humanitarian arguments alone will not change minds in the US, Russia, or China. But they can shore up domestic opposition to testing within nuclear weapons states and give the supporters of the CTBT a strong cause to defend. 

A strong defence of the CTBT does not require states to abandon arguments about verification, international security, and the health of the existing multilateral non-proliferation architecture, but to reconnect to the substantive reasons for the test-ban: not merely that testing is strategically unwise and technically unnecessary, but that the legacies of nuclear testing are so profound that they should not be repeated. 

Framed this way, the test-ban is not only a treaty for governments to uphold but a cause that states, international organisations, and civil society can organise around. International support for the CTBT will be easier to sustain when its technical architecture is understood as serving a broader political purpose – preventing horizontal and vertical proliferation, as well as new humanitarian harm and environmental destruction – rather than as an end in itself. 

If the test-ban is to endure politically, its defence should thus take affected communities seriously as political actors and give greater weight to local populations and civil society – for whom renewed testing represents a repetition of experiences they have already lived through. In many cases, communities affected by nuclear testing generated the pressure that made the issue politically tangible and progress possible, whether in closing test sites or in building support for a global ban on testing. 

If the test-ban is to survive the next 30 years, its defence needs to speak to more than what the CTBT does and how its monitoring system works. It needs to remember why the test-ban emerged in the first place: because nuclear explosions are not simply events to be detected or variables in strategic calculations. They leave lasting consequences for people, communities, and environments. 30 years after the CTBT opened for signature, those consequences should remain central to the case for ensuring that nuclear testing remains unacceptable.

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: Sophie Paris