Hostname: page-component-848d4c4894-ttngx Total loading time: 0 Render date: 2024-06-13T04:33:38.938Z Has data issue: false hasContentIssue false

Just War Theory and the Laws of War as Nonidentical Twins

Published online by Cambridge University Press:  08 December 2017


This essay examines the similarities, but even more the dissimilarities, between (nonrevisionist) just war theory and the laws of war. The similarities are obvious: both just war theory and the laws of war distinguish jus ad bellum from jus in bello, and incorporate the principles of distinction, proportionality, and necessity. The dissimilarities derive from the special character of law. Law needs binary, yes-no standards for drawing lines, for example between armed conflict and lesser forms of violence. Laws come in packages (regimes), so that changing only one law is not always practicable. And legal propositions, unlike philosophical propositions, are often detachable from their reasons and applied in unexpected and unwelcome ways. This is especially important in the stresses of battle, when rules of warfare must be usable “off the shelf” by middle- or lower-ranked personnel with no opportunity for bespoke deliberation. The essay provides contemporary illustrations of these differences.

Roundtable: The Roles of International Law and Just War Theory
Copyright © Carnegie Council for Ethics in International Affairs 2017 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)



1 A point on terminology: by “laws of war” I refer both to international humanitarian law (IHL, the legal jus in bello) and the ad bellum laws governing the use of force.

2 The only place the jus ad bellum enters IHL is in Additional Protocol I's conferring of the belligerent privilege on nonstate actors if they are fighting against racism, colonialism, or foreign occupation (but not otherwise). AP I, Art. 1, § 4.

3 Case Concerning Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. USA), ICJ Reports 1986, p. 94, at § 176. See also Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, ICJ Reports 1996, p. 226, at § 41.

4 The drafters of the Geneva Conventions avoided the word “war” for fear that states would interpret their scope narrowly, as applying solely in declared wars. “Armed conflict” includes both declared and undeclared wars.

5 In some states, the law asks courts to compare the negligence of the plaintiff and the defendant, and apportion damages accordingly; for present purposes, I am ignoring this complication.

6 International Committee of the Red Cross (ICRC), Protocol Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of Non-International Armed Conflicts (Protocol II), June 8, 1977, 1125 UNTS 609, Art. 1(2).

7 How is the Term “Armed Conflict” Defined in International Humanitarian Law? International Committee of the Red Cross Opinion Paper, March 2008,

8 See, e.g., the ICC's Office of the Prosecutor, Situation on Registered Vehicles of Comoros, Greece and Cambodia, Article 53(1) Report, November 6, 2014, §§ 2329 (concluding in § 27 that “the prevalent view in the international community is that Israel remains an occupying power in Gaza despite the 2005 disengagement”).

9 See Guiora, Amos and Luban, David, “Was the Gaza Campaign Legal?ABA National Security Law Report 31, no. 1 (2009), pp. 23 Google Scholar; and Luban, David, “Human Rights Thinking and the Laws of War,” in Ohlin, Jens David, ed., Theoretical Boundaries of Armed Conflict and Human Rights (Cambridge: Cambridge University Press, 2016), pp. 6365 Google Scholar.

10 Prosecutor v. Tadić, ICTY Case No. IT-94-1-I, Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction, October 2, 1995, §§ 66–70.

11 See Ben Emmerson, Report of the Special Rapporteur on the promotion and protection of human rights and fundamental freedoms while countering terrorism, A/68/389, September 18, 2013, § 65. For further discussion, see Daskal, Jennifer C., “The Geography of the Battlefield: A Framework for Detention and Targeting Outside the ‘Hot’ Conflict Zone,” University of Pennsylvania Law Review 161, no. 5 (2013), pp. 1165–234Google Scholar; and Schmitt, Michael N., “Charting the Legal Geography of Non-International Armed Conflict,” International Law Studies 90 (2014), pp. 119 Google Scholar.

12 Cohen, Felix S., “Transcendental Nonsense and the Functional Approach,” Columbia Law Review 35, no. 6 (1935), pp. 809–49CrossRefGoogle Scholar.

13 “The life of the law has not been logic: it has been experience” appears on the first page of Oliver Wendell Holmes's 1881 The Common Law; “considerations of social advantage” is in Holmes, , “The Path of the Law,” Harvard Law Review 10 (1897), p. 467 Google Scholar.

14 Posner, Richard A., “Pragmatic Adjudication,” Cardozo Law Review 18 (1996), pp. 120 Google Scholar.