Rethinking the Law of War Crimes: Targeting Terrorists, Collateral Damage & Military Necessity

The international law of war crimes deviated markedly from the requirements of moral principle (both consequentialist and deontological) on three key issues – proportionality, necessity, and discrimination ‐‐ in ways that are initially puzzling, disconcerting, even distressing. On closer examination, however, these departures make much sense.

The law of proportionality demands that incidental civilian harm to civilian lives and property not exceed any “direct and concrete military advantage anticipated” by the party employing force. Morality is more demanding here than law in their respective restrictions on the use of force, for much moral wrong – causing the variety of harm often rhetorically minimized as “collateral damage” – currently escapes international liability. Many hence criticize the law as too lenient, even complacent in casually indulging human suffering. This moral failure is generally ascribed to considerations of realpolitik, the unwillingness of major military powers to accept more stringent restrictions on their freedom of action in war.

Professional soldiers offer a somewhat different account of the moral‐legal disparity. Like IR “realists,” they are largely unperturbed that law does not fully capture morality’s requirements. Officers wish to preserve a central place in war for martial virtue, their internal professional code, which demands that good soldiers act “beyond the call” of legal duty. The weaker law’s demands, the more ample opportunities arise for its supererogation, for displays of heroism. This professional posture is self‐aggrandizing and inspired by an essentially aristocratic conception of virtue ethics. It is therefore rightly unconvincing to citizens in a modern democracy, committed to the rule of law.

A third and better reason for the present schism between law and morality on collateral damage is simply that we lack sufficient knowledge about how to balance unintended civilian harm against anticipated military advantage. The values at stake may even be incommensurable, insusceptible to measurement along any common metric. At the very least, we need to know more than we now do if we genuinely wish to impose more precise and demanding legal standards on combatants in this area. We are unlikely to make major gains in ethical understanding. The resulting uncertainty is especially vexing when criminal law ‐‐ with its demanding norms of fair warning, a key element of due process ‐‐ becomes our preferred vehicle for ensuring moral accountability within war. In fact, the international regulation of armed conflict now relies increasingly on criminal law, rather than civil. This is due to the many problems discovered over the years with longstanding efforts to impose international liability on states for criminal activity in war.

“Necessity” is the legal duty to employ no more force than essential to victory – tactical, operational, or strategic. It confronts a conundrum similar to proportionality. Morality requires all reasonable efforts to avoid unnecessary harm not only to civilian populations, but also to enemy soldiers. This entails attempting to capture rather than kill them when circumstances permit. Yet despite recent incursions of human rights law onto the terrain of humanitarian law, most courts have interpreted the necessity requirement to demand surprising little of combatants. This seeming laxity is often attributed to the brute power of states to shape the terms of international discussion and thereby limit law’s claims upon them. Only raw realpolitik, on this view, stands between us and the sincere efforts to bring law into closer synch with morality’s legitimate claims upon us.

Yet on closer look, other considerations prove more powerful. We simply know too little about how much material force is truly required to obtain how much battlefield success, much less at the operational and strategic levels. At least, we do not know enough to interpret “necessity” in more exacting ways. The relation of cause and effect in war is simply too obscure. This precludes reliable prediction of what will or won’t bend an enemy to one’s will. Military thinkers concur that considerations of “morale” are no less important than of matériel, and that their respective contributions to success remain too elusive to assess empirically with any exactitude in most circumstances. This is true even after the battle, post facto, hence certainly also ex ante, which is where the law must look in assessing conduct. No one really knows why morale collapses at some times – within the French army in 1940, for instance – any more than why it remains so robust at others, even in extreme adversity. Any claim that a certain measure of force was either dispensable to attaining a certain battlefield aim remains subject to such imponderable vagaries.

When attacking others, belligerents are legally bound to discriminate between combatant and civilian, directly targeting only the former. Here too, however, we quickly find a stark rupture between law from morality, no less troubling than in connection with proportionality and necessity. Yet the problem here, in a sense, is virtually the opposite: morality proves less demanding on use of force than is the law. Morally defensible conduct is often unlawful. This is true, in particular, in regard to targeted killings of terrorist leaders. The moral case for this practice is convincing in many cases. Yet the U.N Charter prohibits such acts almost unequivocally. Customary law offers only a weak, wishful qualification to this conclusion.

The explanation most frequently offered for this moral‐legal split is that states, concerned with ensuring their territorial integrity above all else, oppose any rule authorizing use of force within their borders by others. This reluctance is not only intelligible, but defensible: in a world without any neutral court having compulsory jurisdiction to evaluate invocations of self‐defense, every state would be entitled to act on its own self‐interested (or self‐deceptive) understanding of the threats facing it. Many of these prove exaggerated, even pretexts for simple aggression. As a matter of realpolitik, then, nation‐states – both the more and less powerful – are unwilling to confer legal approval on the practice of targeting terrorists, even as they often tacitly acquiesce in, even privately endorse it. Establishing such a right to target terrorists extraterritorially would diminish their power to control what happens on their soil.

An alternative explanation for the moral‐legal divide is at least equally important, if less readily apparent. We simply do not know what would happen if the international community were to accept such a revolutionary rule. Might it make no practical difference, as IR “realists” would claim? After all, the formal prohibition of targeted killings is not what now most effectively deters weaker belligerents, especially non‐state terrorists, from targeting the leaders of very powerful ones. Or would legalization of targeted killing, i.e., acknowledging the practice as a right available within international law, have harmful unintended consequences, by increasing assassinations of civilian and military leaders throughout the world, including Western democracies? We just don’t know, and are disinclined to take the risks. We engage in the practice, but offer no principled and consistent legal basis for it. As with the law on proportionality and necessity, the chief obstacle to a more ethically‐refined, fine‐tuned law of war crimes proves not to be realpolitik so much as our own cognitive shortfalls, our epistemic deficiencies.

In sum, law and morality ‐‐ as understood through the lens of ideal theory, at least ‐‐ part company with respect to proportionality, necessity, and discrimination, the three central principles of international law on war crimes. In the first and second rules, law demands considerably less than morality, as generally understood. In the third, law demands much more. In all three areas, the conflict between claims of law and of morality arise from the same underlying datum: despite centuries of ambitious effort to place our knowledge of war on a scientific standing, we remain profoundly ignorant of such fundamental and inescapable puzzles as how a given legal change will affect belligerent behavior, what leads to victory or defeat in armed conflict, and how properly to weigh anticipated military gain against foreseeable civilian loss. The existing law of war crimes can be explained and justified only in these terms. In their ambitious bluster, their claims to ever‐increasing mastery of nature, to be on the verge of dispelling war’s perennial “fog,” military thinkers have unwittingly raised the world’s moral expectations of modern belligerents in ways that international law has been right, on closer scrutiny of the facts before them, to disavow.

We are not entirely ignorant, to be sure, at least not equally at all times, on all three issues here examined. It is still possible to spot the “easy cases,” however few. The law is right to confine its attention to these, insisting that we treat them differently than the more frequent, murkier instances of pitiable misfortune and painful fortuities. The upshot is that current international rules on distinction, in particular, should not be abandoned, as many on the Right today would wish (in service of fighting Islamist terrorism). Nor should rules of proportionality and necessity be tautly tightened, as the Left now invariably demands. This book thus offers a modest defense of existing law against several recent, vocal challenges to it from both ends of the political spectrum. In a world where war crimes law is widely chastised by such disparate and influential voices, this humble claim warrants restatement is more careful and rigorous terms than it has received. Because ethical considerations are simply extraneous to it, realpolitik is amoral, at best. In contrast, considerations of human ignorance – the limits of our practical and normative understanding – go to the core of due process rights for those accused of wrongdoing in war. In shifting our explanation for current law from the first to the second set of concerns hence takes us a long ways toward rendering these norms more intelligible and defensible than they now appear to many people throughout the world.