Acknowledgments Introduction I. Three Kinds of Necessity: Exception, License, and Constraint II. A Roadmap III. Normative Prescriptions Part A. Necessity & Jus Ad Bellum Ch. 1. Necessity and the Principle of Last Resort in Just War Theory I. Defining Aggression in the Just War Tradition II. Gentili and the Justification of Offensive War III. Grotius on Fear of Attack IV. The Grotian Principles of Last Resort and Ad Bellum Necessity V. Last Resort as the Ultimate Restraint VI. Equally Efficacious Means Ch. 2. Necessity and the Use of Force in International Law I. Necessity and Customary Treaty Law II. Necessity in Investor-State Relations III. Necessity in Jus ad Bellum Violations IV. Necessity as a Component of Self-Defense V. Conclusion Part B. Necessity & Jus in Bello Ch. 3. Necessity and Discrimination in Just War Theory I. Necessity and Discrimination in Early Modern Just War Theory II. Necessity and Humane Treatment III. Luck and Necessity IV. Military Necessity as a Form of Practical Necessity V. Relating Jus In Bello Proportionality and Necessity Ch. 4. The Foundations of Necessity in IHL I. The ICRC and Necessity II. Lieber's Conception of Necessity III. Necessity in the Nuremberg Tribunals IV. What's Right and What's Wrong with Lieber's Necessity V. Conclusion Ch. 5. Necessity in Human Rights Law and IHL I. Human Rights Necessity II. Combining Human Rights Necessity with IHL Necessity III. Conclusions Ch. 6. Necessity in Criminal Law I. Necessity in Domestic Criminal Law I. No Constraints on the Necessity Defense III. Ad Hoc Constraints IV. Principled Constraints V. Conclusion Ch. 7. Striking a Balance Between Humanity and Necessity I. Humanity II. Humanitarianism and Human Dignity III. Humane Treatment IV. Dignity and Vulnerability V. Humanitarian Rights VI. Concluding Thoughts on the Principles of Humanity and Necessity Part C. Applying Necessity to Contemporary Conflicts Ch. 8. Combatants and Civilians in Asymmetric Wars I. Pirates and Insurgents at War II. Grotius on Non-State Actors in War III. Jus Ad Bellum Issues IV. Jus In Bello Issues V. Civil Wars and Civilians Ch. 9. Disabling vs. Killing in War I. Specific Prohibitions versus General Duties II. The Hors de Combat Argument III. Least Harmful Means Test at the Geneva Negotiations IV. Should Jus in Bello Require Disabling before Killing? VI. Necessity and Killing Fleeing Soldiers Ch. 10. The Duty to Capture I. Is Capture Required by Jus in Bello Necessity? II. Are Different Rules for Civilians and Combatants Morally Legitimate? III. Capture as a Requirement of Constitutional Necessity IV. The Moral Arguments for a Duty to Capture Ch. 11. Force Protection I. Understanding Force Protection II. Jus ad Bellum Necessity and Force Protection III. Jus in Bello Necessity and Force Protection IV. The Hannibal Procedure V. Reasonable Force Protection Conclusion Index

this volume contains valuable insights and provocative proposals that consistently take into account integrated legal and moral considerations. Ohlin and May leave the tangled cluster of meanings of 'necessity' far clearer than they were - a major accomplishment.

"this volume contains valuable insights and provocative proposals that consistently take into account integrated legal and moral considerations. Ohlin and May leave the tangled cluster of meanings of 'necessity' far clearer than they were - a major accomplishment." -- Henry Shue, Criminal Law and Philosophy "The challenge that they took on was immense, and although the book occasionally betrays its origin in two distinct treatments, the result of their labor is a valuable guide to the ways in which necessity has shaped and been shaped by international law." -- Grotiana 39 "Necessity, as the authors observe in their opening sentence, is arguably the most powerful concept in the law'. It is of central importance in the law of war, in human rights law, and in both domestic and international criminal law. Yet it is a deeply confusing notion because it can function variously as a justification for harming, an excuse for having engaged in wrongful harming, and as a constraint on harming that is, it can defeat what would otherwise be a justification for harming. In this brilliantly illuminating book, the authors systematically untangle the many ways in which necessity operates in both morality and law, and on the basis of their analyses draw a range of conclusions of considerable significance, particularly for the practice of war. This is a book of great scholarly and practical importance." - Jeff McMahan, Whites Professor of Moral Philosophy, University of Oxford "Necessity is a slippery concept, at once enabling and limiting. Necessity justifies power but also purports to limit its employment. In their characteristic thoughtfulness and erudition, Ohlin and May explore the many uses and abuses of necessity across legal fields, including the use of force, the conduct of hostilities, human rights, and international criminal law. It is a first-of-its-kind study, topical and urgent, a must read not only for students of international law, but also for anyone interested in jurisprudence more broadly." - Gabriella Blum, Rita E. Hauser Professor of Human Rights & Humanitarian Law, Harvard Law School "Much mischief is done under the cloak of necessity. This deeply interdisciplinary analysis highlights this cluster concepts dangers while imaginatively exploring its possibilities for modestly constraining the killing of combatants as well as noncombatants." - Henry Shue, Senior Research Fellow at the Centre for International Studies, University of Oxford "What does necessity permit? No concept in the law carries greater moral gravity and few have caused as much moral confusion. Ohlin and May offer a tour de force survey of the conceptual structure of necessity in international law. An indispensable contribution to a long-troubled problem." - John Fabian Witt, Allen H. Duffy Class of 1960 Professor of Law & Professor of History, Yale Law School "Jens David Ohlin and Larry May are world-class experts in the laws of armed conflict. Here, they turn their attention to the vexed concept of necessity in wartime . . . using clear language, conceptual analysis, historical reference, and mastery of international law to get at the true sense . . . [They apply] rich reference to the most helpful historical thinkers as well as contemporary legal rulings and cases . . . One arrives at the end with a much better understanding of the idea of military necessity, and of the relevant laws." - Brian Orend, Professor of Philosophy, Director of International Studies, University of Waterloo "Jens David Ohlin's and Larry May's book provides a timely and very important analysis of one of the foundational principles of these bodies of law: necessity. This impressive work provides a unique and fresh perspective. It analyzes the meaning of necessity not just in legal terms, but also deeply probes its moral and normative underpinnings. There has not been sufficient discussion about the degree to which human rights law should or can effectively regulate the violence associated with armed conflict. This work presents an important starting place for any analysis about whether human rights law is up to the task being demanded of it by some in the international legal community. This book should be required reading for anyone seeking to unravel what at times seem to have become intractable ideological debates about how the various bodies of law operate to control the use of force in contemporary conflict." - Ken Watkin, Lawfare

Selling point: Traces all the various uses of the concept of necessity in international law Selling point: Aims to determine whether there is any over-arching unity to these uses across the various sub-disciplines Selling point: Discusses necessity in international humanitarian law (IHL) Selling point: Focuses on the concepts of necessity as exception, necessity as license, and necessity as regulation Selling point: Applies philosophical investigations to determine whether the law ought to be revised or not

Jens David Ohlin is Professor of Law and Associate Dean for Academic Affairs at Cornell Law School. He specializes in international law and criminal law. He specifically focuses on the laws of war with special emphasis on the effects of new technology on the waging of warfare, including unmanned drones in the strategy of targeted killings, cyber-warfare, and the role of non-state actors in armed conflicts. He authored The Assault on International Law (Oxford, 2015). Larry May is the W. Alton Jones Professor of Philosophy, Professor of Law, and Professor of Political Science at Vanderbilt University. He has published over thirty books, including book length studies of each of the four crimes under the ICC's jurisdiction. These books have won awards in philosophy, law, and international relations. He has also published extensively on the history of the just war tradition, especially on the work of Grotius and Hobbes. He co-authored Proportionality in International Law (with Michael Newton, Oxford, 2014), and Limiting Leviathan: Hobbes on Law and International Affairs (Oxford, 2013).

Selling point: Traces all the various uses of the concept of necessity in international law Selling point: Aims to determine whether there is any over-arching unity to these uses across the various sub-disciplines Selling point: Discusses necessity in international humanitarian law (IHL) Selling point: Focuses on the concepts of necessity as exception, necessity as license, and necessity as regulation Selling point: Applies philosophical investigations to determine whether the law ought to be revised or not