Lex Mundi Nova Webinar Series
The ICJ Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons 30 Years On: What Legacy and What Now?
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The Lex Mundi Nova webinar series explores the legacy of the landmark 1996 Advisory Opinion of the International Court of Justice (ICJ) on the Legality of the Threat or Use of Nuclear Weapons. By examining the ruling itself, the shifts in international law and new science in the last three decades, and emerging technological and geopolitical risks—from nuclear testing, to AI, to warfare in space—the series will ultimately consider whether the ruling’s ambiguities and gaps can and should be resolved in light of today’s legal and evidentiary realities.
With partners and expert panelists from around the world, the series will examine key developments in international law since 1996 relevant to the legality of nuclear weapons including international humanitarian law (IHL), international human rights law (IHRL), international environmental law (IEL), and the rights of future generations, against the backdrop of significant new scientific evidence of the humanitarian, environmental, and socio-economic consequences of nuclear weapons.
The series will consider the progress and setbacks in fulfilling the Court’s unanimous ruling that States are under an obligation to pursue in good faith and conclude negotiations to achieve nuclear disarmament in all its aspects. It will also probe the Court’s controversial decision to leave a critical question unresolved: whether the threat or use of nuclear weapons would be lawful or unlawful in an extreme circumstance of self-defense where a State’s survival is at stake.
Finally, the series will consider the legal obligations that may be triggered by emerging and complex risks, such as artificial intelligence in nuclear command, control and communications systems, and the placement of nuclear weapons in outer space.
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Webinar 1 – 16 April 2026
The ICJ Advisory Opinion (AO) 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 AO 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 AO and what are those today of international law constraining nuclear weapons?
Panel
Opening remarks – Prof. Nico Krisch, Head, International Law Department, Geneva Graduate Institute
The story of the 1996 ICJ AO, its key findings and gaps, and its legacy – Phon van den Biesen, Co-President, International Association of Lawyers Against Nuclear Arms (IALANA), retired public interest lawyer, Amsterdam
How have the knowledge of nuclear weapons impacts, treaties, policies, politics, and public perceptions changed since 1996? – Seth Shelden, General Counsel and United Nations Liaison, International Campaign to Abolish Nuclear Weapons (ICAN), New York
Key developments in international law constraining nuclear weapons – Ilya Ilanov, Doctoral Researcher, University of Geneva
Gendered perspectives of international law constraining nuclear weapons – 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), and Louise Arimatsu, Distinguished Policy Fellow, Centre for Women, Peace and Security, LSE
WATCH the replay here.
Webinar 2 – 7 May 2026
Nuclear weapons and the protection of the environment: developments in science and international law since the 1996 ICJ Advisory Opinion
While the 1996 ICJ AO highlighted the relevance of international environmental law (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?
Panel
Opening remarks – Chuck Johnson, Policy Director, International Physicians for the Prevention of Nuclear War – Geneva Liaison Office
Nuclear fallout from the use of nuclear weapons – Sébastien Philippe, Assistant Professor of Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison
The impacts of a nuclear war on the climate and on global food supply – Lili Xia, Assistant Research Professor, Department of Environmental Sciences, Rutgers University
The use of nuclear weapons under the lens of international environmental law including climate law – Manasa Venkatachalam, Independent Legal Consultant in public international law and climate justice
The use of nuclear weapons under the lens international humanitarian law protecting the environment – Helen Obregon, Senior Legal Adviser, International Committee of the Red Cross (ICRC)
WATCH the replay here.
Webinar 3 – 21 May 2026
Nuclear weapons and human rights: developments in science and international law since the 1996 ICJ Advisory Opinion
The 1996 ICJ AO 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, how has international law evolved? 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?
Panel
Opening remarks – Prof. Michèle Olivier, University of Stellenbosch
What we know today about the public health impacts of nuclear war – Dr Andrew Haines, Professor of Environmental Change and Public Health, London School of Hygiene and Tropical Medicine
Nuclear weapons under the lens of international human rights law – Simon Walker, Chief, Rule of Law and Democracy Section, Office the United Nations High Commissioner for Human Rights
From the ICJ to lived experience: a survivor-centred approach, intergenerational harm, and the role of economic, social, cultural, and disability rights in the pursuit of nuclear justice – Aigerim Seitenova, Co-founder, Qazaq Nuclear Frontline Coalition
The rights of future generations and nuclear weapons – Ashfaq Khalfan, Director of the Sustainability Regulation Observatory, London School of Economics and Political Science
WATCH the replay here.
Webinar 4 – 27 May 2026
The obligation to pursue good faith negotiations leading to the total elimination of nuclear weapons, thirty years after the ICJ’s Advisory Opinion
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”. Yet beyond its response to the question put to it, the Court made a 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?
Panel
Opening Remarks – Celine Nahory, Director of Government Relations and Advocacy, ICAN
The state of play of nuclear disarmament negotiations, 30 years after the ICJ AO – Hans Kristensen, Federation of American Scientists
Assessing fulfillment of the obligation to negotiate nuclear disarmament in good faith – John Burroughs, Lawyers Committee on Nuclear Policy (LCNP) and International Association of Lawyers Against Nuclear Arms (IALANA)
Good faith negotiations leading to the total elimination of nuclear weapons – Professor Scott Sagan, Caroline S. G. Munro Memorial Professor of Political Science and Senior Fellow at the Freeman Spogli Institute for International Studies, Stanford University
Making sense of nuclear disarmament in the polycrisis age – Nick Ritchie, University of York
WATCH the replay here.
Webinar 5 – 11 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), thirty years after the ICJ Advisory Opinion
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?
Panel
Opening Remarks – Dr. Deepshikha K. Vijh, Executive Director, The Lawyers Committee on Nuclear Policy
Jus ad bellum and jus in bello in the 1996 ICJ AO and today: separation or conflation? – Dr. Jasmine Moussa, Member of the Permanent Court of Arbitration
Can the right of self-defence ever release a State from its obligations under international law? – Marcelo Kohen, Professor Emeritus, Geneva Graduate Institute
How nuclear deterrence policies hold up to international law in the 1996 ICJ AO and today – Kimiaki Kawai, Vice Director and Professor, Research Centre for Nuclear Weapons Abolition, University of Nagasaki
The legality of self-defence with nuclear weapons in the new global order – Professor Antony Anghie, National University of Singapore Faculty of Law, and University of Utah S.J. Quinney College of Law
WATCH the replay here.
Webinar 6 – 7 July 2026 18:00 EDT | 8 July 2026 07:00 JST / 10:00 FJT/NZT
Emerging Risks, Emerging legal frameworks: Looking to the future on the 30th Anniversary of the ICJ Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons
In the first five webinars of the Lex Mundi Nova series, we examined the past and the present: stories from architects of the 1996 ICJ Advisory Opinion (AO) campaign and assessments of the AO’s ongoing impact, analyses of international humanitarian, human rights, and environmental law and science with respect to the lawfulness of nuclear weapons, Nuclear Weapons States’ legally binding disarmament obligations as set forth in both the NPT and the 1996 AO, and the very legality of nuclear deterrence policies. The sixth and final webinar in the Lex Mundi Nova Webinar Series will be held on July 8, 2026, the 30th anniversary of the 1996 ICJ Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons (Pacific Time). In this discussion, we will be examining both individually, and at their convergence, emerging nuclear risks, and emerging legal frameworks to constrain them: AI in NC3 systems, the militarization of space, the climate-nuclear nexus, and humanitarian constraints on testing, threat, and use through the lens of both indigenous peoples’ and children' s rights.
Panel
AI in NC3 systems: A legal and ethical analysis of the militarization of AI and its impact on nuclear risk – Emily Crawford, Deputy Head of School and Dean, Sydney Law School
The 1967 Outer Space Treaty, the Law of Armed Conflict, and the practices of nations: What constrains the placement of nuclear weapons in space? – David Koplow, Scott K. Ginsburg Professor of Law, Georgetown Law
Reparative justice for Pacific nations regarding nuclear weapons testing, and the nuclear weapons-climate nexus – Dr. Milla Vaha, Deputy Head of School (Postgraduate and Higher Degree Research) University of the South Pacific
The rights of children against nuclear weapons testing and use and emerging research on the humanitarian effects of nuclear weapons on children and young people – Tim Wright, AsiaPacific Director, ICAN
WATCH the replay here.
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