Many thanks to Derek Jinks for his kind words on the article and deeply incisive comments. I will do my best to reply sequentially to the provocative issues he’s raised.
1. I agree that conceptual overlap of ad bellum and in bello does not necessarily pose a problem for IHL. Indeed, as Jinks says, some discrepancy based on the nature of the parties is foundational to IHL, most prominently, the privileges and rights of state soldiers and the correlative prohibition on purposive violence by most private armies, which, unlike those of states, do not presumptively enjoy the combatant’s privilege. (Long footnote: I think that I disagree, however, with the ICRC Commentary’s view that soldiers fighting a war of aggression should be denied combatant immunity. I’m unsure of the context of this part of the Commentary. But I can’t recall an instance in which this proposition has received support in either state practice or opinio juris, or even, for that matter, de lege ferenda scholarship. None of the Nazis, for example, were tried for simple murder rather than war crimes, and it’s doubtful whether aggression remains a crime under customary international law. It should not be, in my view, but that’s an even longer digression. One of the principal rationales for the DA is the absence of a neutral arbiter, and any effort to identify one party as the aggressor and deny that party combatant immunity would, I think, foreseeably lead to the breakdown of IHL rules in the conflict.) The principal worry that I have about the influence of ad bellum considerations on in bello rules may be illustrated by a question I pose about the Kosovo campaign, an example that I flesh out in the article. To avert misunderstanding, I should state at the outset that I support NATO’s action under the circumstances and do not think the ICTY Prosecutor erred by declining to investigate NATO. But strictly in terms of the in bello legality of NATO’s conduct of that campaign, it seems to me that modern IHL requires belligerents to assume at least some risk (how much is debatable) to themselves to reduce the risk of death and suffering to enemy civilians. Yet NATO, by instructing its pilots to fly at a minimum height of 15,000 feet, deliberately reduced the risk to its own forces to zero at the cost of a substantial increase in the risk to Serbian civilians. Suppose NATO’s avowed ad bellum objective had been to annex and occupy Serbia (rather than to halt incipient ethnic cleansing). Would we be so quick to dismiss NATO’s in bello conduct of the war as lawful? I concede this is speculative, but it seems to me that our ad bellum appraisal of NATO’s conduct as humanitarian intervention influenced our in bello appraisal of how it conducted the military campaign.
2. In terms of the evidence: I suggest that the DA has been misconstrued or misapplied, sometimes deliberately, but more often subconsciously or tacitly—in part because of natural self-serving biases. I doubt that any belligerent would openly claim that the justice of its cause relieves it of or relaxes the in bello constraints under which it must conduct warfare (although, notably, the Soviet Union, North Vietnam, and others, in the past, and more recently, the United States, in part, in its conduct of the “GWOT” have made essentially this claim). But the gravamen of the article’s argument is that the DA is customary international humanitarian law as the prohibition on torture is CIL: there’s far more state practice than we acknowledge that’s in tension with the rhetoric and written word affirming the DA. The law-in-action, as Roscoe Pound famously put it, may well differ from the law-on-the-books—and in subtle ways. That doesn’t mean violations of the norms against torture or of the DA are lawful. But the examples of state (and non-state) practice and jurisprudence I supply seem to me to share, at bottom, a tendency to elide the DA. Readers of the article will make their own judgment. I concede I may be wrong, or exaggerating the extent of the trend. I hope that’s true.
3. Jinks’s point here is well-taken, and to a certain extent, the article does try to make the case that we need to tinker with the ad bellum, as it’s currently construed—for, at present, in my judgment, it encourages violations of the DA. That’s why I spend so much time critiquing the ICJ’s jurisprudence of war despite the fact that it seldom opines on IHL. The Court has a distinct institutional role in the international system and sees itself as the guardian of the U.N. Charter’s regime on force, so I don’t mean to fault the ICJ as much as may seem at first glance. The ICJ, however, is emblematic, in my view, of a trend toward eliding, rather than candidly confronting, the twenty-first century challenges of warfare. For as long as it insists on hewing to an anachronistic state-to-state paradigm, it encourages a divergence or disconnect between the law and the reality of modern warfare. As I say at the outset of the article, “the efficacy and normative force of the law of war is roughly commensurate to its correspondence to the nature and felt necessities of warfare.” It must be possible for elite belligerents operating in good faith to abide by IHL and still feel they can do their job, i.e., win or accomplish a military objective. “Insofar as [in bello-ad bellum] conflation obscures the need to refine the law of war to adapt to current sociopolitical conditions and to work out practical conceptions of [e.g.,] both ad bellum and in bello proportionality, it impedes the ability of international law to develop at both ends of the duality. To preserve the DA axiom in the twenty-first century therefore may well require reform of both in bello and ad bellum law. (For example, as I argue in the article, the law of war should decisively adopt the aggregative, rather than the atomized, conception of ad bellum proportionality: it’s both more realistic and reflects a more just balance between the competing values at stake.)
4. Here I have to punt—as I largely do in the article’s conclusion raising these points. It seems to me that there are, or will foreseeably be, situations in which, as I say, the very same humanitarian values that underwrite the modern DA may countenance limited exceptions to it—for example, if a war fought in technical violation of the DA is the sole politically feasible way to halt an incipient genocide. Conflicts of theoretically harmonious values—between the humanitarian imperative of the DA and the equally, if not (I would think) more, compelling need finally to cease the hypocrisy of saying “never again” and yet turning a blind eye to genocides—require political choices that I hesitate to opine on in the abstract.
5. Jinks is absolutely right to point to the difficulty in incorporating IHRL in the context of an armed conflict, while respecting the DA. The convergence of IHL and IHRL pointed out in Meron’s well-known article on the humanization of IHL will increasingly raise the kinds of questions that Jinks flags. Candidly, I haven’t thought these issues through well enough to respond in any depth. But I would say, in response to the example Jinks raises, that even though Iraq clearly qualified as the aggressor in 1990, that would not render every detention or killing of a Kuwaiti soldier an arbitrary deprivation of life or liberty in violation of IHRL. To say otherwise, I think, would be to deny the DA, and the consequences of that for IHL would be detrimental for both IHL and IHRL—and the relationship between the two. The circumstance of armed conflict, as the Nuclear Weapons decision rightly, in my judgment, said, alters what it means for a deprivation of life or liberty to be “arbitrary” within the meaning of, say, the ICCPR.
6. In the realm of proportionality, it’s very difficult to avoid allowing the ad bellum to influence the in bello. In theory, as just war theorists like Jeff McMahan and Thomas Hurka have argued, there’s a slippery slope from “concrete and direct military advantage” to “victory.” The challenge is for IHL to prevent the former from slipping into the latter, for if the relevant yardstick is “victory,” every in bello strike’s proportionate in theory. It’s for that reason that AP1, for example, uses the words “concrete” and “direct,” and enjoins a commander to determine whether such a military advantage (not ultimate victory) would be “excessive” relative to the civilian harm it will foreseeably cause. But the sorts of inquiries raised by the Prosecutor’s Report on Kosovo, reproduced on page 111 of the article, urgently need to be answered. That’s another article, but absent further work in this area, the kind of confusion about proportionality that reigned in the Israel-Hezbollah conflict will persist—as will the needless death and suffering caused by it.
Once again, my sincere thanks to Opinio Juris, YJIL, and Professor Derek Jinks. I welcome comments: rdsloane [at] bu [dot] edu.