Lex Mundi Nova
Webinar Series 2026
The Lex Mundi Nova webinar series explored 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 ultimately considered 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 examined 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 considered 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 also probed 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 considered 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.
The ICJ Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons 30 Years On: What Legacy and What Now?
The ICJ Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons 30 Years On: What Legacy and What Now?
The Lex Mundi Nova webinar series explored 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 ultimately considered 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 examined 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 considered 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 also probed 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 considered 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.
IN PARTNERSHIP WITH
WEBINAR 1 | APRIL 16, 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?
OPENING REMARKS
Professor Nico Krisch
Head, International Law Department, Geneva Graduate Institute
PANEL
Phon van den Biesen
The Story of the 1996 ICJ AO, Its Key Findings and Gaps, and Its Legacy
Co-president, International Association of Lawyers Against Nuclear Arms (IALANA), retired public interest lawyer, Amsterdam
Seth Shelden
How Have the Knowledge of Nuclear Weapons Impacts, Treaties, Policies, Politics, and Public Perceptions Changed Since 1996?
General Counsel and United Nations Liaison, International Campaign to Abolish Nuclear Weapons (ICAN), New York
Ilya Ilanov
Key Developments in International Law Constraining Nuclear Weapons
Doctoral Researcher, University of Geneva
Christine Chinkin and Louise Arimatsu
Gendered Perspectives of International Law Constraining Nuclear Weapons
Christine Chinkin is 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 is a Distinguished Policy Fellow, Centre for Women, Peace and Security, LSE IL
WEBINAR 2 | May 7, 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?
OPENING REMARKS
Chuck Johnson
Policy Director, International Physicians for the Prevention of Nuclear War, Geneva Liaison Office
PANEL
Sébastien Philippe
Nuclear Fallout From the Use of Nuclear Weapons
Assistant Professor of Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison
Lili Xia
The Impacts of a Nuclear War on the Climate and on Global Food Supply
Assistant Research Professor, Department of Environmental Sciences, Rutgers University
Manasa Venkatachalam
The Use of Nuclear Weapons Under the Lens of International Environmental Law Including Climate Law
Independent Legal Consultant in public international law and climate justice
Helen Obregon
The Use of Nuclear Weapons Under the Lens of International Humanitarian Law Protecting the Environment
Senior Legal Adviser, International Committee of the Red Cross (ICRC)
WEBINAR 3 | May 21, 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?
OPENING REMARKS
Professor Michèle Olivier
University of Stellenbosch
PANEL
Dr. Andrew Haines
What We Know Today About the Public Health Impacts of Nuclear War
Professor of Environmental Change and Public Health, London School of Hygiene and Tropical Medicine
Simon Walker
Nuclear Weapons Under the Lens of International Human Rights Law
Chief, Rule of Law and Democracy Section, Office the United Nations High Commissioner for Human Rights
Aigerim Seitenova
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
Co-founder, Qazaq Nuclear Frontline Coalition
Ashfaq Khalfan
The Rights of Future Generations and Nuclear Weapons
Director of the Sustainability Regulation Observatory, London School of Economics and Political Science
WEBINAR 4 | May 27, 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?
OPENING REMARKS
Celine Nahory
Director of Government Relations and Advocacy, ICAN
PANEL
Hans Kristensen
The State of Play of Nuclear Disarmament Negotiations, 30 Years After the ICJ AO
Federation of American Scientists
John Burroughs
Assessing Fulfillment of the Obligation to Negotiate Nuclear Disarmament in Good Faith
Lawyers Committee on Nuclear Policy (LCNP) and International Association of Lawyers Against Nuclear Arms (IALANA)
Professor Scott Sagan
Good Faith Negotiations Leading to the Total Elimination of Nuclear Weapons
Caroline S. G. Munro Memorial Professor of Political Science and Senior Fellow at the Freeman Spogli Institute for International Studies, Stanford University
Nick Ritchie
Making Sense of Nuclear Disarmament in the Polycrisis Age
University of York
WEBINAR 5 | June 11, 2026
Are Nuclear Weapons at the Vanishing Point of the Laws of War? The legality of nuclear weapons under the law of self-defense (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-defense 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-defense? 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?
OPENING REMARKS
Dr. Deepshikha K. Vijh
Executive Director, The Lawyers Committee on Nuclear Policy
PANEL
Dr. Jasmine Moussa
Jus ad Bellum and Jus in Bello in the 1996 ICJ AO and Today: Separation or conflation?
Member of the Permanent Court of Arbitration
Marcelo Kohen
Can the Right of Self-defence Ever Release a State From Its Obligations Under International Law?
Professor Emeritus, Geneva Graduate Institute
Kimiaki Kawai
How Nuclear Deterrence Policies Hold Up to International Law in the 1996 ICJ Advisory Opinion and Today
Vice Director and Professor, Research Centre for Nuclear Weapons Abolition, University of Nagasaki
Professor Antony Anghie
The Legality of Self-defense with Nuclear Weapons in the New Global Order
National University of Singapore Faculty of Law, and University of Utah S.J. Quinney College of Law
WEBINAR 6 | July 7, 2026
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
Emily Crawford
AI in NC3 Systems: A legal and ethical analysis of the militarization of AI and its impact on nuclear risk
Deputy Head of School and Dean, Sydney Law School
David Koplow
The 1967 Outer Space Treaty, the Law of Armed Conflict, and the Practices of Nations: What constrains the placement of nuclear weapons in space?
Scott K. Ginsburg Professor of Law, Georgetown Law
Dr. Milla Vaha
The Cultural and Political Rights of Indigenous Communities as a Constraint on Nuclear Weapons Testing, Threat, and Use, and the Nuclear Weapons-climate Nexus
Deputy Head of School (Postgraduate and Higher Degree Research) University of the South Pacific
Tim Wright
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
AsiaPacific Director, ICAN