This is the second part in a two-part series on the international legality of nuclear threats. The first part of this report, Nuclear Threats Under International Law Part I: The Legal Framework, can be accessed here.

Anna Hood and Monique Cormier examine the international legality of threats to use nuclear weapons. Based on their review of existing prohibitions against nuclear weapons in international law, the authors determine whether they can be applied to threats of nuclear use. The article explores the concept of unilateral negative security assurances, language and prohibitions in international agreements, and when states can legally use force against one another.

This special report was prepared for the project “Reducing the Risk of Nuclear Weapon Use in Northeast Asia.” The research described in this paper was co-sponsored by the Research Center for Nuclear Weapons Abolition, Nagasaki University (RECNA), the Nautilus Institute for Security and Sustainability, and the Asia-Pacific Leadership Network for Nuclear Non-Proliferation and Disarmament (APLN), with collaboration from the Panel on Peace and Security of Northeast Asia (PSNA). MacArthur Foundation and New Land Foundation funding to Nautilus Institute supported this project.

This report is published simultaneously by the Nautilus Institute here and by RECNA-Nagasaki University here. This report is published under a 4.0 International Creative Commons License the terms of which are found here. It was first published in the Journal for Peace and Nuclear Disarmament here.

Click here to learn more about the project. Below is the report abstract.

Abstract

Throughout the nuclear age, states have made a wide array of threats to use nuclear weapons. There is, however, often little clarity as to whether such threats are legal or illegal under international law. This article is the second in a two-part series, and in this piece we examine how two specific sets of international legal rules apply to select examples of past nuclear threats. In particular we analyse the legality of certain threats under the jus ad bellum regime of international law that regulates recourse to war between states, before turning to consider specific threat examples in the context of the jus in bello regime, which applies to regulate the conduct of hostilities during an armed conflict. Throughout the article, we identify a number of complexities and deficiencies in the ways that the rules of jus ad bellum and jus in bello apply to nuclear threats in practice.

Keywords: Nuclear weapons; international law; threat of force; nuclear threat

About the Author

Dr Anna Hood is an associate professor at the University of Auckland’s Faculty of Law. Her research focuses primarily on international law and security, and international disarmament law. Within international disarmament law she has particular expertise in, and has published widely on, nuclear weapons law. She is the co-editor, with Dr Treasa Dunworth, of the book Disarmament Law: Reviving the Field (Routledge, 2020) and she has been awarded multiple grants for her work on international disarmament law. In addition to her academic research, Anna provides international law advice to a range of civil society organisations, think tanks and governments.

Dr Monique Cormier is a Senior Lecturer in the Monash University Faculty of Law. Her primary research interests include jurisdiction and immunities in international law and legal issues relating to nuclear non-proliferation. Recent publications include The Jurisdiction of the International Criminal Court over Nationals of Non-States Parties (Cambridge University Press, 2020) and ‘Can Australia Join the Nuclear Ban Treaty without Undermining ANZUS?’ (Melbourne University Law Review, 2020, co-authored with Anna Hood).

Disclaimer: The opinions articulated above represent the views of the author(s) and do not necessarily reflect the position of the Asia Pacific Leadership Network or any of its members. The APLN’s website is a source of authoritative research and analysis and serves as a platform for debate and discussion among our senior network members, experts and practitioners, as well as the next generation of policymakers, analysts and advocates. Comments and responses can be emailed to apln@apln.network.

Image: New Zealand Representatives at the International Court of Justice in the Hague