Jens David Ohlin and Larry May: Necessity in international law.

• Author: Tully, Stephen
• Position: Book review

Jens David Ohlin and Larry May

Necessity in International Law

(Oxford University Press, 2016) ISBN 978-0-19-062293-0,276 pages.

War is a forced contest of violence between belligerents. Destructive power ought to be unleashed only when truly necessary. This book contends that war could be rendered more humane, for combatants and civilians alike, by codifying a slightly more restrictive understanding of the principle of necessity (p 276).

In their introduction, the authors consider that the concept of necessity "is often the key element that drives the outcome of the analysis", whether it be with respect to individual self-defence under national criminal law, national self-defence under international law or killing during armed conflict (p 1). Necessity "is not a one-size-fits-all concept" (p 273). The authors begin by conceptualising three distinct senses of necessity: as an excuse or exception to an otherwise binding obligation or pre-existing rule (the "dangerous version of necessity"); as a licence to engage in certain conduct that is otherwise consistent with generally applicable laws because such action is part of a broader role; and finally as a constraint on government action that blocks activity. Accordingly, military necessity is a licence under international humanitarian law, international and national criminal law seek to confine the exception version of necessity, and the concept of necessity is at its most constrained under international human rights law.

The authors commence with general principles to articulate how necessity works in the jus ad bellum and jus in bello. They then apply those general lessons to specific controversies regarding the appropriate rules for conducting hostilities in a contemporary armed conflict, including against non-State actors and terrorists. Part A of the book focuses on necessity in the context of the use of force under international law and the principle of last resort in the just war tradition. Part B considers necessity in the context of international humanitarian law, criminal law and international human rights law, the relationship between necessity and discrimination in just war theory, and how to strike a balance between necessity and humanity. Part C applies necessity to several topical issues of contemporary conflicts, with discussion first given to the familiar dilemma of distinguishing between combatants and civilians in asymmetric wars where one side deploys force without using a...