The ICJ Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons 30 Years On: What Legacy and What Now?
Lex Mundi Nova Webinar Series
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Exploring the legacy of the landmark 1996 Advisory Opinion (AO) of the International Court of Justice on the legality of the threat or use of nuclear weapons, the Lex Mundi Nova webinar series will examine the AO’s impact on legal, political, and ethical debates in a world markedly more dangerous than that of thirty years ago.
With partners and a collection of expert panelists from around the world, Lex Mundi Nova will examine what the court said, what was left unsaid, and its controversial decision to leave a critical question unresolved: whether the use of nuclear weapons might be lawful in an extreme circumstance of self-defense where a State’s survival is at stake. This ambiguity has endured for three decades, influencing state practice, nuclear doctrines, and the evolution of international law.
We will also examine the vast expansion in both scientific evidence of the humanitarian, environmental, and socio-economic consequences of nuclear weapons, and the key developments in international law relevant to the legality of the possession, testing, threat, and use of nuclear weapons, including international human rights and environmental law and the rights of future generations. Finally, we will examine the impact of emerging and complex risks, including artificial intelligence in nuclear command systems and the prospect of nuclear weapons placement in outer space.
The Lex Mundi Nova webinar series will ultimately probe whether the ruling’s enduring ambiguities can or should be resolved in light of today’s legal and factual realities.
Webinar Registration
Webinar 1 – 16 April 2026
The ICJ Advisory Opinion on the legality of the threat or use of nuclear weapons: What did it achieve, what did it leave open, and how have law, practice, and perceptions changed?
What were the origins of the campaign that led to the 1996 ICJ Advisory Opinion and how did it play out? What were the Court’s key findings, based on “the current state of international law, and of the elements of fact at its disposal”? What did the Court leave unsaid? What has changed in international law and practice since? And in public perceptions? What were the structural biases of the 1996 ICJ Advisory Opinion and what are those today of international law constraining nuclear weapons?
Speakers
Phon van den Biesen, Co-President, International Association of Lawyers Against Nuclear Arms (IALANA), retired public interest lawyer, Amsterdam
Seth Shelden, General Counsel and United Nations Liaison, International Campaign to Abolish Nuclear Weapons (ICAN), New York
Ilya Ilanov, University of Geneva
Christine Chinkin, Professor of International Law and founding Director of the Centre for Women, Peace and Security, London School of Economics and Political Science (LSE)
Louise Arimatsu, Distinguished Policy Fellow, Centre for Women, Peace and Security, LSE
Register HERE
Webinar 2 – 6 May 2026 (to be confirmed)
Nuclear weapons and the protection of the environment: what has changed in science and international law since the 1996 ICJ AO, and what has not?
While the 1996 ICJ AO highlighted the relevance of IEL to the question of the legality of the use of nuclear weapons, it merely concluded that IEL “indicates important environmental factors that are properly to be taken into account” when implementing IHL. Thirty years later, how have those “important environmental factors” evolved? What does new science say about the environmental impacts of nuclear weapons? IEL has expanded considerably over the last thirty years, notably in the area of “climate law”. How do these IEL developments further constrain the legality of nuclear weapons? How have IHL rules protecting the environment been strengthened?
Speakers
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Register HERE
Webinar 3 – 30 Years Later: Protecting Human rights - May 2026
Nuclear weapons and human rights: what has changed in science and international law since the 1996 ICJ AO, and what has not?
The 1996 ICJ AO very briefly addressed the human rights constraints on the threat or use of nuclear weapons through the sole prism of the right to life, and concluded that whether a particular loss of life in war is an arbitrary deprivation of life can only be decided by reference to IHL. Thirty years later, what does new science say about the impacts of nuclear weapons on human health, including on the descendants of first-generation survivors? What are the new developments in international human rights law of relevance to the legality of nuclear weapons? How do inter-generational rights and the rights of indigenous peoples further constrain nuclear weapons? And to what extent do human rights continue to apply in war?
Speakers: To Be Announced
Registration Opens on April 15, 2026
Webinar 4 – The “Unanimous” Obligation to Disarm - May 2026
The obligation to pursue good faith negotiations leading to the total elimination of nuclear weapons.
It has been said that, as a result of the Court’s ambiguous response to the question of the legality of the threat or use of nuclear weapons, the ICJ AO “is likely to become all things to all States and fail to influence State conduct” (D. Akande, 1997). Yet beyond its response to the question put to it, the Court made a fairly clear and unanimous finding that States have an obligation to pursue and conclude negotiations in good faith “leading to nuclear disarmament in all its aspects under strict and effective international control”. How has the conduct of States, in particular nuclear-armed States, been influenced, if at all, by this part of the ICJ’s AO? How is the fulfilment of this obligation to be appraised, notably “good faith” efforts? And how does it fit in the context of the transition to a new global order?
Speakers: To Be Announced
Registration Opens on May 15, 2026
Webinar 5 – The “Exception” for Self-Defence and Deterrence Policies - June 2026
Are nuclear weapons at the vanishing point of the laws of war? The legality of nuclear weapons under the law of self-defence (jus ad bellum) and the law of armed conflict (jus in bello).
In its 1996 AO, the ICJ famously held that the threat or use of nuclear weapons would generally be contrary to the principles and rules of international law applicable in armed conflict, but that in view of the state of international law at the time and of the facts at its disposal, it could not conclude definitively on the lawfulness or unlawfulness of such threat or use “in an extreme circumstance of self-defence in which the very survival of the State would be at stake”. How have the facts and the law about the threats and use of nuclear weapons changed since the 1996 AO? If it is extremely doubtful that nuclear weapons could ever be used in accordance with the principles and rules of IHL, is it ever lawful to use nuclear weapons in self-defence? Can jus ad bellum ever override jus in bello? If deterrence policies imply a threat to use nuclear weapons, under what conditions would a threat to use nuclear weapons be considered legal?
Speakers: To Be Announced
Registration Opens on May 15, 2026
Webinar 6 – Testing, Space, AI, and the Legality of Nuclear Weapons in Peacetime - June 2026
Beyond the threat and use of nuclear weapons in war: how international law constrains nuclear weapons activities in peacetime, and whether and how it can respond to emerging threats including AI and the placement of nuclear weapons in space.
The 1996 ICJ AO was focused on the legality of the threat and use of nuclear weapons in armed conflict. That same year, the UN General Assembly adopted the Comprehensive Test Ban Treaty, which has not since yet entered into force, and has been challenged by incidents or allegations of nuclear testing, or expressions of intent to test. Likewise, the 1967 Outer Space Treaty’s prohibition to place nuclear weapons in space has been challenged by certain nuclear-armed States threatening such placement. In addition, the use of artificial intelligence (AI) in nuclear command, control and communications systems (NC3) is heightening the risk of use of nuclear weapons by accident or miscalculation. Could the new developments in international law over the last thirty years be applied to successfully mitigate these threats to people and the planet, i.e. from nuclear weapons testing or placement in outer space, and from AI NC3?
Speakers: To Be Announced