Abstract This Article argues there is a legal duty to disobey illegal nuclear strike orders. Failure to carry out this duty may result in criminal and civil liability. Because nuclear weapons are quantitatively and qualitatively different from conventional weapons, typical legal calculations regulating their use under the laws of war or humanitarian law, as well as human rights law, change along with the change in weaponry. Abstract At least five "unique characteristics" of nuclear weapons ominously distinguish them from conventional weapons in ways that promise only to increase civilian death and suffering. First, quantitatively, the blast power, heat, and energy generated far outstrip that of conventional weapons, likely rendering nuclear weapons indiscriminate. Second, qualitatively, the radiation released is so powerful that it damages DNA and causes death and severe health defects throughout the entire lives of survivors as well as their children. Third, nuclear weapons make virtually impossible humanitarian assistance to survivors at the blast scene struggling to survive, leading to more suffering and death. Fourth, damage to the environment may produce not only devastating environmental harm itself but also widespread famine and starvation. Fifth, nuclear weapons cause long-lasting multi-generational psychological injury to survivors of the blast. Abstract All of these factors weigh heavily against the humanitarian goals of the law of war and human rights law, which are designed chiefly to prevent and reduce civilian death and suffering. These humanitarian and human rights rules require distinction between combatants and civilians, proportionality in attack, military necessity, prevention of unnecessary suffering and superfluous injury, and prevention of the arbitrary loss of life. This Article's thesis largely boils down to: If conventional weapons can be used to achieve the same or similar military objectives as nuclear weapons in proximity to civilians, and nuclear weapons are ordered to be used instead, that order may be manifestly illegal, leading to war crimes for which actors can be liable if they obey the illegal order. This universal customary international law applies both to state and non-state actors alike. The destructive power of nuclear weapons cannot be contained in either space or time. Moreover, what are the practical and theoretical implications of the answers to these questions? Are we talking about merely an affirmative defense to a domestic charge of not following orders? Or, perhaps, something of greater symbolic, real world, and legal value to the international system as a whole regarding how international law does and should treat the use of nuclear weapons around the globe. That is, an international legal framework applicable to all states-and even non-state actors-that holds specific personnel accountable for following illegal orders, even if the legality of nuclear weapons themselves as a general matter has not yet been definitively resolved. . But as we shall see, infra Part IV.A., as a treaty, once it enters into force it will bind only states parties. Moreover, those states most affected by the treatynamely, nuclear weapons states-have refused to support the treaty ban and have rejected it as a broader norm-forming instrument necessary for the creation of general or "customary" international law. Both because this repudiation of the treaty is by the most powerfully affected states, and because the objections come at the genesis of the potential norm-formation, these nuclear "persistent objector" states stunt a broader, non-treaty prohibition on nuclear weapons under customary international law or, if such a norm were to form, it would not apply to the objecting states. See Dino Kritsiotis, On the Possibilities of and for Persistent Objection, 21 DUKE J. OF COMP. & INT'L L. 121, 129-30 (2010) . To be sure, the very fact that these states have both updated their nuclear arsenals and maintained their right to use nuclear weapons is strong evidence This Article proposes a novel account of the law's relationship to nuclear weapons. Thus far, the great bulk of policy and legal conversation regarding nuclear weapons has addressed in blanket fashion whether their use is david98@example.org. But the International Court of Justice (ICJ) has refused to categorically outlaw their use, 3 and the reality is that states (and perhaps non-state actors) presently possess nuclear weapons and have expressed a willingness to use them. Accordingly, this Article addresses the different question of whether certain nuclear strikes would be illegal if nuclear weapons were used. And, further, whether there is a legal duty to refuse to carry out an illegal strike order, as well as the implications of any such duty-such as susceptibility to criminal prosecution or civil liability for serious violations of international law, like war crimes and the arbitrary deprivation of life. Hence it is important at the outset to understand what this Article is and is not about: It is not advocating the outlawing of nuclear weapons across the board. Formal international institutions combined with components of customary international law have largely settled that question, at least for the time being. This Article is also not a policy piece about the strategic use of nuclear weapons, examining, say, the desirability of deterrence through nuclear weapon stockpiling or the role that mutually assured destruction plays in preventing a nuclear holocaust. Rather, the Article's argument is fundamentally legal and comprises at least three key questions: (1) when is a nuclear strike order illegal; (2) is there a legal duty to disobey the illegal order; and (3) what are the implications of refusing to disobey the order? As a preliminary matter, the analysis does not contend that all uses of nuclear weapons are necessarily illegal. For purposes of the Article, nuclear weapons, like all weapons, are permissible unless they contravene the laws of war or what is called international humanitarian law. 4 There may be some situations in which the use of nuclear weapons does not contravene the laws of war. For instance, the ICJ mused about "the use of nuclear weapons by a State in an extreme circumstance of self-defense, in which its very survival is at stake" 5 -a scenario that ties into the discussion of "belligerent reprisals" later in the Article. 6 Others have argued that "use of a low yield nuclear weapon against warships on the High Seas or troops in sparsely populated areas" that the components necessary to form customary international law are lacking, as also discussed infra at Part IV.A. In the absence of a solid prohibition on their use, nuclear weapons remain-the Nuclear Weapons Ban Treaty notwithstanding-legal for non-states parties to the treaty, i.e., those states that actually possess and therefore may use nuclear weapons. Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 1996 I.C.J. Rep. 226, ¶ 21 (July 8) [hereinafter Advisory Opinion] . 3 See Advisory Opinion, 1996 I.C.J. at ¶ 97. 4 Id. ¶ 21. 5 Id. ¶ 97. 6 Infra Part IV.B.5. might be legal under international law. 7 These situations occupy a legal limbo where the use of nuclear weapons might be legal but also might not necessarily be illegal-in short, their legality under international law would be contested. 8 Instead of dwelling in this limbo, the Article concentrates on "clearly" or "manifestly" illegal nuclear strikes for which liability attaches and, in this regard, seeks to be a referent for commanders and soldiers tasked with the use of nuclear weapons in proximity to civilian populations. Part II begins by articulating the origins of a duty to disobey illegal orders and elaborates the "clearly" or "manifestly" illegal standard. Next, Part III explains why nuclear weapons have unique destructive powers, both quantitatively and qualitatively, as opposed to conventional weapons. The discussion of why nuclear weapons are uniquely destructive sets the stage for the Article's principal thesis in Part IV: Under international humanitarian and human rights law, if conventional weapons can be used near a civilian population to achieve the same or similar military objectives as nuclear weapons, then it would most likely be manifestly illegal to use nuclear weapons. And, as such, liability would generally attach to a commander who fails to disobey a nuclear-strike order in this situation. One possible exception to liability attaching would be the doctrine of "belligerent reprisals." As will be discussed, while the strike itself would remain illegal, it may nonetheless be justified under this doctrine and, accordingly, the doctrine may offer an affirmative defense to liability. 9 Part V then discusses the chain of command in ordering a nuclear strike and issues of immunity, starting with the head of state on down. For only those with sufficient information to refuse an illegal order can be held liable under basic rule-of-law principles, so an individual's position in the chain of command partly determines his liability risk. Finally, Part VI confronts the problem of non-state actors. It concludes that they are subject to the same standards and duties as state actors due to the universal nature of customary international law and international humanitarian and human rights law in particular, which are designed to prevent and minimize loss of civilian life. II. The Duty to Disobey A. The Duty The duty to disobey an illegal order to launch a nuclear weapon originates in international law's rejection of the defense that an individual is excused from 7 Advisory Opinion, 1996 I.C.J. at ¶ 91 (quoting the United Kingdom, Written Statement before the Court, ¶ 3.44). 8 Customary international law is largely an empirical phenomenon reliant upon the practice of states, including entering into treaties, to define the contours of its rules. The office of this paper will be strikes that are clearly or manifestly illegal at the core of established rules of humanitarian law. Absent a universally or near universally ratified treaty, the legality of the peripheral gray area scenarios could be discerned only by some additional data, in the form of actual strikes and reactions thereto by states. 9 See infra Part IV.B.5. liability because he followed "superior orders." A. The Duty 10 Colloquially put, the defense goes something like this: "I cannot be liable for carrying out an illegal act because I was simply following orders." At least since the Nazis were prosecuted for war crimes and crimes against humanity at Nuremberg, this defense has largely disintegrated. I say "largely" because the argument may sometimes be used as a mitigating circumstance where, for example, the court determines that justice so requires. A. The Duty 11 But because those atop the chain of command are most likely to be in the best position to question and refuse an illegal order to use nuclear weapons, 12 it is hard to imagine this mitigating situation adhering in the context of launching a nuclear strike. A. The Duty In language that became pregnant for international humanitarian and human rights law instruments and jurisprudence, the Nuremberg Charter explicitly rejected the superior-orders defense. Article 8 provides: "The fact that the Defendant acted pursuant to order of his Government or of a superior shall not free him from responsibility, but may be considered in mitigation of punishment if the Tribunal determines that justice so requires." A. The Duty 13 Similar language appears in Manual. 18 As C. Robert Kehler, former Commander of U.S. Strategic Command (STRATCOM) explains, U.S. soldiers are "bound to question (and ultimately refuse) illegal orders." 19 Yet, presaging the discussion below of the standard that applies when holding actors accountable for refusing to disobey illegal orders, 20 both the Rome Statute and U.S. law require more than just the receipt of orders that are merely legally debatable as to legitimate disobedience. As we will see, this heightened threshold comports well with real-world practice. A. The Duty Before addressing this heightened standard, it is important to clarify why disintegration of the superior-orders defense has birthed a duty and, incidentally, a right to disobey an illegal order to launch a nuclear strike. The reason is straightforward: If an actor does not refuse to disobey the illegal order, he or she violates the law and can be held liable. Both international and domestic law make plain that subordinates are not to carry out illegal orders. As the remainder of the Article shows, when it comes to nuclear strikes, those orders are likely to result in serious violations of international law, such as war crimes, for which actors can be held criminally and civilly accountable. In short, any command to break the law is ultra vires and gives rise to liability, which subordinates have a duty and a right not only to avoid but also to reject. What that law is and how it operates will be the subject of Part IV. B. The Standard But how to tell whether to impose liability and thus whether a duty arises? Yes, the order must be illegal-but how illegal? The entire structure of military command and efficacy would crumble if subordinates started second-guessing orders that they deemed of marginal or debatable legality. The standard adopted by the ICC and the U.S. military provides that the order must be "manifestly unlawful," 21 or constitute "clearly illegal orders to commit violations of the law of war." 22 Hence the threshold for disobeying an order is higher than just an arguably illegal order. 23 It means knowing, or being reasonably expected to know, that the order is illegal and does not hinge upon solely contextual or situational judgments. 24 Put another way, the relevant mens rea is that superior orders are not a defense if the actor knows or should know that the order is manifestly illegal, or grossly deviates from what a reasonable person knows or should know; the order must be illegal on its face. 25 The U.S. Department of Defense manual cites as examples orders to "fire upon the shipwrecked" or to "kill defenseless persons who have submitted to and are under effective physical control" of U.S. forces. 26 It would also include the targeted murder of innocent civilians. For instance, if a soldier were ordered to shoot a baby in the head, that would be manifestly illegal and any subordinate should know it is illegal. It is this threshold that must be kept in mind as we move forward into the unique characteristics of nuclear weapons, the relevant international law governing armed conflicts, and the decisions made by those who have the power and the information to effectively launch nuclear weapons. 26 In short, where conventional weapons can be used in proximity to civilians to achieve the same or similar military objectives instead of nuclear weapons, an order to use a nuclear weapon would be manifestly illegal and anyone with sufficient factual knowledge regarding the circumstances of the order should know it. In turn, that person has both a duty and a right to disobey the nuclear strike order. All of this hinges, of course, on knowing why and how nuclear weapons are different. III. Nuclear Weapons Are Different As the ICJ has recognized, and as science and experience demonstrate, nuclear weapons are different from conventional weapons. According to the ICJ, nuclear weapons have "certain unique characteristics" resulting from the release of "not only immense quantities of heat and energy, but also of powerful and prolonged radiation," 27 with the latter being "peculiar to nuclear weapons." 28 In other words, there is a "qualitative as well as quantitative difference between nuclear weapons and all conventional arms." 29 These differences render nuclear weapons not only uniquely catastrophic, but also uniquely unpredictable. Indeed, ("The distinguishing mark of a "manifestly unlawful order" should fly like a black flag above the order given, as a warning saying 'Prohibited.' Not formal unlawfulness, hidden or half-hidden, nor unlawfulness discernible only to the eyes of legal experts, is important here, but a flagrant and manifest breach of the law, definite and necessary unlawfulness appearing on the face of the order itself, the clearly criminal character of the acts ordered to be done, unlawfulness piercing the eye and revolting the heart, be the eye not blind nor the heart not stony and corrupt, that is the measure of "manifest unlawfulness" required to release a soldier from the duty of obedience upon him and make him criminally responsible for his acts."). 26 LOW MANUAL, supra note 18, at 1049. 27 Advisory Opinion, 1996 I.C.J. at ¶ 35. 28 Id. Importantly, I exclude here the ICJ's holding that nuclear weapons may be lawful in "an extreme circumstance of self-defence in which the very survival of a state may david98@example.org." Id. ¶ 97. 29 Id. ¶ 86. III. Nuclear Weapons Are Different as the ICJ aptly and forebodingly put it, "[t]he destructive power of nuclear weapons cannot be contained in either space or time." 30 While some debate among experts exists as to whether a particularly lowyield nuclear bomb might have a smaller blast yield than the most powerful conventional bomb, 31 it is commonly accepted that nuclear weapons generally produce heat and energy that far exceed the capabilities of any conventional weapon, no matter how powerful. 32 Unlike conventional weapons, which certainly can cause tremendous destruction (think the firebombing of Dresden), nuclear weapons create a fireball that forms in less than a millionth of a second at several tens of millions of degrees, vaporizing all matter into gas or plasma. There is no opportunity to plan for or escape the attack as in a comparatively "slow motion" firebombing; the nuclear detonation instantaneously incinerates everything in its path. 33 Hence, quantitatively, the potential for destruction and the resulting loss of human life from a nuclear weapon differ from conventional weapons. This affects the law-of-war or humanitarian law calculi discussed in Part IV.B, as a matter of sheer blast power, scope, and detonation timing. III. Nuclear Weapons Are Different Yet perhaps the most distinct feature of nuclear weapons is their qualitative differences from conventional weapons. Nuclear weapons release massive amounts of thermal and ionizing radiation. As Stuart Casey-Maslen notes, the effects of this radiation on the body are "prodromal, hematologic, gastrointestinal, pulmonary, cutaneous and neurovascular." 34 well as cancer during and subsequent to childhood. 43 Again, these uniquely extensive effects of radiation have major consequences for the law-of-war calculi in Part IV.B; namely, principles of distinction, proportionality, military necessity, and prevention of unnecessary suffering. 44 It is also uncontroversial that ionizing radiation would make extremely difficult, if not impossible, any meaningful humanitarian response to a nuclear attack, effectively stranding those most in need-a position long held by both the World Health Organization and the Red Cross and Red Crescent movement 45 -further compounding and magnifying the suffering of victims, in both degree and number. Relatedly, the radiation released by a nuclear bomb is enormously unpredictable since it promises to cover a tremendous geographic area and is variously dependent upon uncertain factors like shifting weather patterns and atmospheric conditions, to which the bomb itself may significantly contribute. 46 Which leads into the dire environmental harms that major nuclear explosions or exchanges may generate, 47 causing depletion in, among other things, the ozone layer, farming, and food production, thereby potentially resulting in famine. 46 48 This is due in large part to the dispersal of dirt and dust, (2015) ("In reality, whilst calling for greater efforts at the international level as regards response to [nuclear] events, the authors recognize that the chances are near to zero of bringing effective assistance to victims of large-scale use of [nuclear] weapons."); Ruff, supra note 35, at 812 ("It is important in this context to emphasize that no effective humanitarian response is possible for even a single nuclear weapon detonated in a population centre, let alone nuclear war, as has been the unequivocal conclusion of the World Health Organization and the International Red Cross and Red Crescent Movement for many years . . . ."). 46 See infra notes 47-50 discussing environmental harms generated by nuclear detonation. 47 I say may generate because there is the possibility of a surgical nuclear strike that does not severely impact the environment. This is contingent upon the strike not triggering escalation in the use of nuclear weapons. Because the command and control apparatus is unable to foresee whether the surgical strike will in fact produce escalation, the law-of-war calculation as to environmental damage is necessarily a post-hoc inquiry in this situation. As such, it poses an interesting question for those ordered to use nuclear weapons in a comparatively discrete manner. It seems contrary to the rule of law to hold actors accountable for the unpredictable environmental effects of a single, low yield nuclear strike that fails to severely impact the environment since liability would essentially be retroactive because the effect-escalation-is not necessarily predictable. contamination of water supplies by radioactive residuals, and the consequent deterioration of both plant and animal life, posing a very real and widespread risk of starvation for many millions of people. 49 In fact, using nuclear weapons for major attacks targeting cities or other highly populated areas could cause short term or even prolonged (decadal) nuclear winters for large civilian populations. 50 Finally, as informative as the cold hard science is, no account of the uniquely devastating effects of nuclear detonations would be complete without taking into consideration the actual human experiences, views, and psychological damage to those who have survived such attacks. In Japan, the survivors of the atomic blasts at Hiroshima and Nagasaki comprise a distinct class, referred to as hibakusha. One of the foremost experts on the effects of nuclear exposure is the hibakusha Dr. Masao Tomonaga. He survived the detonation of the second atomic bomb on August 9, 1945 in Nagasaki and has had a long and distinguished medical career documenting human health and other harmful consequences resulting from the bombings. 51 Dr. Tomonaga recounts the horror of the experience itself and the lingering fears it instilled in survivors; namely, "[a]fter the initial wave of elevated rates of leukaemia, which continued for about fifteen years, a second wave of solid cancerous tumors began. Increased occurrence of these cancers still continues today and causes great suffering for atomic bomb survivors and their families." 46 52 Similarly, Mr. Yoshiro Yamawaki, also a hibakusha of Nagasaki, describes not only the terrible experience of the detonation which haunts him daily and the reverberating impact of the radiation on his psyche and well being, but also what he believes are deadly transgenerational ripples. In his words: "The effects go on across generations to the children and grandchildren of survivors, carrying on the cruelty of using these weapons. I have four daughters, and my oldest daughter has a type of disease that is similar to leukemia. My second daughter is suffering from breast cancer." 53 However, the scientific data do not conclusively show trans-generational medical harm passed to children who were not in utero at the time of the detonation. 46 Which does not discount the very real trans-generational mental harms caused by nuclear weapons and their radiation ripples into future generations. 46 calamity in the history of armed conflict were the atomic bomb attacks on the Japanese cities of Hiroshima and Nagasaki in August of 1945."). 49 Maresca & Mitchell, supra note 48, at 641. Some might argue that this environmental harm qualifies as a breach of Article 35(3) of Additional Protocol I, which prohibits "methods or means of warfare which are intended, or may be expected, to cause widespread, long-term and severe damage to the natural environment"; see also Advisory Opinion, 1996 I.C.J. at ¶ 35. 50 See generally R. P. Turco, O. B. Toon, T. P. Ackerman, J. B. Pollack & Carl Sagan, Nuclear Winter: Global Consequences of Multiple Nuclear Explosions, 222 SCIENCE 1283 222 SCIENCE (1983 . 51 After the Atomic Bomb, supra note 42, at 507 (interview with Dr. Masao Tomonaga). 52 Id. at 509. 53 Id. at 524 (interview with Mr. Yoshiro Yamawaki). Mr. Yamawaki's attribution may well be the result of a lingering psychological harm and very real perceived physical harm originating his daughter's disease. See infra notes 54-58. If his first daughter, on the other hand, was alive or in utero at the time of the bombing, her disease could be considered a direct effect of the bombing itself. 46 Robert Lifton explains that for survivors of Hiroshima and Nagasaki " [t] here is real fear about transmitting radiation effects to subsequent generations, because it is known to be possible." 54 This is "even though a systematic increased incidence of birth defects in the next generation has not been demonstrated in control studies." 55 Lifton also points out that survivors of the bombs at Hiroshima and Nagasaki suffer severely from what he terms "psychic numbing." 46 56 In Lifton's words, " [b] ased on all evidence, of Hiroshima and everything else we know, the numbing and listless behavior-no panic but a kind of listless, slow motion as in Hiroshima-would likely be so extreme among that tiny contingent of survivors [of a nuclear bomb] that people would be numb to the point of immobilization." 57 Compounding these effects are the stigma and discrimination felt by survivors (indeed, in Japan they have their own special name) who fear deformation and disease will be passed on to their blood lines. This fear destroys deep-seated psychological comfort in "living on in our children and their children," severing the chain of life. 58 In sum, at least five "unique characteristics" of nuclear weapons ominously distinguish them from conventional weapons in ways that promise to increase civilian death and suffering. First, quantitatively, the blast power, heat, and energy generated far outstrip that of conventional weapons. Second, radiation released is so powerful that it damages DNA, causing death and severe health defects throughout the lives of survivors as well as their children exposed in utero. Third, nuclear weapons make virtually impossible humanitarian assistance to survivors at the blast scene struggling to survive, leading to more suffering and death. Fourth, damage to the environment may cause not only devastating environmental harm itself but also widespread famine and starvation. And fifth, nuclear weapons cause long-lasting, multi-generational psychological injury to survivors of the blast. All of these factors weigh heavily against the humanitarian goals of the law of war, which is designed chiefly to prevent and reduce civilian death and suffering. IV. Law A. Baselines Before jumping into the specifics of international humanitarian and human rights law, some foundations, or baselines, from which to build my argument should be laid out. A. Baselines A somewhat preliminary baseline is that the law of war goes by a few names; it also may be called the law of armed conflict or international 54 Robert Lifton, Beyond Psychic Numbing: A Call to Awareness, 52(4) AMER. J. ORTHOPSYCHIATRY 619, 621 (1982) . 55 Id. 56 Id. at 623. 57 Id. 58 Id. at 626. humanitarian law. The term international humanitarian law will be used throughout the rest of the Article to alliteratively partner it with the related but distinct field of human rights law. While humanitarian law governs the conduct of hostilities, human rights law applies everywhere and to everyone. 59 Put differently, while armed conflict triggers humanitarian law, human rights law is ever present and ever applicable, regardless of situation-including armed conflict. The concurrent jurisdiction furnished by these two overlapping bodies of law gives rise to the possibility of conflicts of law. Yet, as discussed in more detail below, 60 the more specific lex specialis of humanitarian law tends to inform and complement the governing standards of human rights law during armed conflict, such that human rights law effectively adopts, or is heavily informed by, international humanitarian law for certain wartime rules. 61 Another baseline is that humanitarian and human rights law are quintessentially international law. 62 To underestimate the importance of this baseline would be a serious and ultimately very confusing mistake. It is true that these laws are often incorporated into domestic law, 63 but their source and substance derive not from domestic lawmaking apparatuses but instead from international law. 64 59 Here I take a customary international law view of human rights rather than a strict treaty-based view under which, according to the U.S. position, only states are obliged to uphold human rights abuses within their respective territories or under their effective control. Under customary law, all human beings have certain fundamental rights-including the right not to be arbitrarily deprived of life-that may be enforced against individual defendants, see infra Part IV.C. While a traditional view of human rights involved the state qua state's obligation to individuals, recent developments like the prolific U.S. Alien Tort Statute litigation have made clear, even in the United States, that individual human beings (and perhaps private corporations) can be liable for depriving other human beings of fundamental human rights. These rights are also not limited to a state's territory but rather apply everywhere, since "there is no jurisdictional limitation to the reach of international human rights law, at least as it applies to nuclear weapons." Casey-Maslen, supra note 34, at 666. 60 See infra notes 124-127, acknowledging the debate surrounding this topic but adopting the ICJ view in the Advisory Opinion so as to move the Article forward. 61 ARMED CONFLICT 3 (2016) . However, I do not have the space to fully explore it in this Article. As I discuss in Part IV.C, below, because the ICJ adopted the view of lex specialis articulated above in its Advisory Opinion, see Advisory Opinion, 1996 I.C.J. at ¶ 25, I adopt it here for purposes of moving the discussion forward. 62 Advisory Opinion, 1996 I.C.J. at ¶ 75; see also infra note 63. 63 LOW MANUAL, supra note 18, at 1059-60. 64 Treaty law is probably the easier to comprehend because it can crudely be analogized to a contract: states contract (treaty) with each other to provide certain humanitarian and human rights protections. If a state breaches the contract, other states may similarly breach or take counter-measures against the breaching state to either bring it into compliance or kick it out of the contractual community (treaty regime). Finally, as with a contract, the treaty does not bind states that have not assented to, or, in international legal speak, ratified, the agreement. A. Baselines Custom is trickier. It is comprised of two elements: (1) state practice; and (2) opinio juris-that is, the intent or belief that the practice arises out of a sense of legal obligation. Unlike treaty law, this form of international law is not like a contract. Quite the contrary, its law binds all states regardless of whether they have ratified a treaty. As a binding customary law for all states, and indeed, all actors everywhere, it may be thought of as a universal law that covers the globe. In fact, there are some offenses-including war crimes-that give rise to what is called "universal jurisdiction," meaning any state in the world has jurisdiction to prosecute the perpetrators. 65 To satisfy the state-practice component of customary international law, the practice must be consistent and widespread; and although the precise threshold for widespread is as yet unresolved, there must at a minimum be a supermajority of states that agree to and follow the rule consistently. 66 The opinio juris component can be gleaned from official statements and actions demonstrating that states follow the practice out of a sense of legal obligation and not just for purely political or expedient ends. This is sometimes referred to as the "psychological" element of the customary law equation because it purports to get into the mind of the state and communicate its thinking. 67 While obviously relying in large part on a fictional anthropomorphization of the state (since states tend not to be While it may be difficult to prove state practice with respect to nuclear weapons for the same reason it is difficult to prove a negative, the absence of their use by states points to a practice of, at minimum, restraint. It should also be noted that treaties themselves may, in certain circumstances, constitute strong evidence of custom because they represent the state practice of entering into the treaty and the opinio juris of treating the terms of that treaty as legally binding. 67 monolithic in their decision-making), the psychological element nonetheless may be a useful heuristic for understanding what is meant by opinio juris. Now, generally speaking, a state may treaty around the default customary rule in the same way parties may contract around a default common law rule. But there are some norms of customary international law that cannot be circumvented by treaty. These mandatory rules are called jus cogens, or peremptory norms of international law. 68 They are mostly framed in terms of prohibitions: no genocide, no torture, no crimes against humanity, no war crimes. 69 Thus a state cannot decide, on its own, to opt out of these prohibitions. Nor can it treaty with another state to do the same. It would be as if Hitler and Mussolini entered into an agreement to exterminate ethnic minorities. Jus cogens would immediately swoop in to invalidate that treaty from the start. It is necessary to stress again, however, that these norms are framed in the nature of prohibitions: no genocide, no war crimes, etc. They have little if anything to say about if and how liability attaches to a violation of the norm-just that there is a violation of international law. This is of crucial importance to the discussion of belligerent reprisals below 70 because it may synthesize jus cogens with other doctrines humanitarian law which authorize otherwise unlawful conduct, at least insofar as liability is concerned. A. Baselines A final baseline: there is a difference between the law of going to war (jus ad bellum) and the humanitarian law of how one conducts war (jus in bello). 71 This Article is principally concerned with the latter-how hostilities are conducted-because that is the realm in which an illegal strike order would be handed down. Put another way, even if a nuclear-strike order would start a legally authorized war (jus ad bellum), it is a separate question whether the strike order itself is a legal means of conducting the military action (jus in bello). 71 In short, humanitarian and human rights law are distinct but related strands of international law, which may be based in treaty or custom. If the law is customary, then it applies to all states and, Part VI argues, also to non-state actors. Indeed, customary international law covers the entire globe and applies to everyone (that is, after all, the entire point of a truly international law). Although not every state has ratified the most relevant treaties governing humanitarian law-in particular Additional Protocol I to the Geneva Conventions-certain principles of humanitarian and human rights law have passed into custom. Accordingly, the major question for the next section is: "What types of orders to detonate nuclear weapons are manifestly illegal under international humanitarian and human rights law?" B. Humanitarian Law Four fundamental principles govern international humanitarian law: distinction between combatants and civilians, proportionality, military necessity, and the prevention of unnecessary suffering. These principles are classed in the jus in bello category and any serious violation of humanitarian law is considered a war crime. 75 The differences between nuclear weapons and conventional weapons alter the analysis of each principle under humanitarian law. The result is that an order to launch a nuclear weapon is legally distinct from an order to launch a conventional weapon. Since the nuclear launch order is legally distinct, or at least produces legally distinct real-world outcomes, it invites a distinct legal analysis that may well yield a different legal outcome. It is an analysis and an outcome with which those responsible for deploying nuclear weapons ought to be intimately familiar because it can mean the difference between a lawful strike and a humanitarian or human rights violation and, consequently, the difference between following a legal nuclear strike order and a duty and right to disobey an illegal one. B. Humanitarian Law Before getting into specifics, the difference between legal standards and legal rules should be emphasized. A legal rule is a hard and fast line, the content and application of which are easy to administer-think: "Do not exceed the speed limit." Either one exceeds the speed limit or one does not. 3. In addition to the grave breaches defined in Article 11, the following acts shall be regarded as grave breaches of this Protocol, when committed wilfully, in violation of the relevant provisions of this Protocol, and causing death or serious injury to body or health: B. Humanitarian Law (a) Making the civilian population or individual civilians the object of attack; (b) Launching an indiscriminate attack affecting the civilian population or civilian objects in the knowledge that such attack will cause excessive loss of life, injury to civilians or damage to civilian objects, as defined in Article 57, paragraph 2 (a) (iii); (c) Launching an attack against works or installations containing dangerous forces in the knowledge that such attack will cause excessive loss of life, injury to civilians or damage to civilian objects, as denned in Article 57, paragraph 2 (a) (iii); (d) Making non-defended localities and demilitarized zones the object of attack; (e) Making a person the object of attack in the knowledge that he is hors de combat; (f) The perfidious use, in violation of Article 37, of the distinctive emblem of the red cross, red crescent or red lion and sun or of other protective signs recognized by the Conventions or this Protocol. B. Humanitarian Law advantage of ex ante clarity and administrative efficiency, but they often give rise to after-the-fact exceptions when challenged. A legal standard, by contrast, is a purposefully flexible and context-specific guiding principle, the content and application of which are more situational-think: "Drive reasonably." Both the rule and the standard would prohibit driving recklessly but the standard may permit, say, going above the speed limit to get someone in urgent need to the hospital, while the rule unambiguously prohibits it. Much of humanitarian law is essentially standard based. That is, while the principles may sometimes sound like rules in a vacuum, their application in real life is contextual. Thus, what constitutes a "proportional" attack under humanitarian law will depend on the precise situation on the ground, the military advantage expected, the probability and degree of expected civilian deaths, and-crucially-the type of weapon used. 76 As largely a collection of standards, humanitarian law mostly lacks the situational clarity that rules enjoy. Rather, as noted, application of humanitarian law standards is highly contextual. As such, there is less certainty at the moment an order is handed down that the order would be illegal under the laws of war. Accordingly, holding an individual to a strict legal-versus-illegal line in the sand would be both unfair and unrealistic given the pressures and need to obey orders generally in situations of armed conflict, lest the entire edifice of military effectiveness disintegrate. Rather, as already noted, 77 the needle moves in favor of a presumption of an order's legality, such that to refuse the order it must be "manifestly illegal," not merely of arguable legality. 78 The manifestly illegal standard not only creates an affirmative defense to the charge of disobeying orders in military proceedings; 79 it also insulates defendants from borderline or even sensationalist allegations of war crimes since in any armed conflict there is a high probability of civilian death, some of which may be permissible under international law. Distinction The principle of distinction or protection of civilians not taking part in hostilities is in many ways the wellspring of all humanitarian law principles. A famous formulation is found in Additional Protocol I of the Geneva Conventions (which embodies customary law 80 ): Distinction 76 See, e.g., id., art. 57(2)(a)(ii) ("With respect to attacks, the following precautions shall be taken: those who plan or decide upon an attack shall . . . take all feasible precautions in the choice of means and methods of attack with a view to avoiding, and in any event to minimizing, incidental loss of civilian life, injury to civilians and damage to civilian objects." In order to ensure respect for and protection of the civilian population and civilian objects, the Parties to the conflict shall at all times distinguish between the civilian objects and military objectives and accordingly shall direct their operations only against military objectives. 81 As their names suggest, military personnel and military objects contribute to military action and objectives. The destruction, capture, or neutralization of such action and objectives must be designed to offer a direct military advantage and must not target civilian populations. 82 To adhere to the principle of distinction, military forces must refrain from using means and methods that strike without distinction near a civilian population. Moreover, the methods or means of attack must protect against effects that cannot be limited as required by international humanitarian law, 83 a point to which we will return below. 84 This is often referred to as the prohibition on indiscriminate attacks 85 -a humanitarian law that attends the bedrock distinction principle. 81 Nuclear weapons have the potential to annihilate this bedrock distinction principle. If civilians are within the radius of the immense blast yield, they will be incinerated along with military personnel and objectives. 86 Unlike conventional weapons, which can more accurately target military personnel and objectives, nuclear weapons indiscriminately pulverize anything in their detonation zone, 81 Additional Protocol I, supra note 75, art. 48. Similarly, Article 51(2) provides: "The civilian population as such, as well as individual civilians, shall not be the object of attack. Acts or threats of violence the primary purpose of which is to spread terror among the civilian population are prohibited." And J.I. Henckaerts and L. Doswald-Beck explain: 81 The parties to the conflict must at all times distinguish between civilians and combatants. Attacks may only be directed against combatants. Attacks must not be directed against civilians . . . . The parties to the conflict must at all times distinguish between civilian objects and military objectives. Attacks must not be directed against civilian objects. (a) those which are not directed at a specific military objective; (b) those which employ a method or means of combat which cannot be directed at a specific military objective; or (c) those which employ a method or means of combat the effects of which cannot be limited as required by this Protocol; and consequently, in each such case, are of a nature to strike military objectives and civilians or civilian objects without distinction. J.I. HENCKAERTS & DOSWALD-BECK, CUSTOMARY INTERNATIONAL LAW OF WAR 3 (2005 which promises to be far larger than that of any conventional weapon. Furthermore, the ionizing radiation emanates well beyond the blast yield, killing and harming innocent civilians (as well as their unborn children). The breadth of effects caused by a nuclear blast means that it would be difficult to say it was "directed" against the military objective around which civilians are located, especially in contradistinction to conventional weapons. In brief, a nuclear blast in any area with a civilian population would almost by definition manifestly violate the cardinal principle of distinction where a conventional weapon option is available, and would thus constitute a war crime. J.I. HENCKAERTS & DOSWALD-BECK, CUSTOMARY INTERNATIONAL LAW OF WAR 3 (2005 Here an analogy can be made to biological weapons, which the international community has outlawed. 87 To borrow a phrase used by the ICJ in the context of nuclear weapons, biological weapons also cannot be contained in space or time. Like the indiscriminate and unpredictable consequences geographically and temporally of biological weapons on civilian populations, the repercussions of nuclear weapons are extraordinarily unpredictable and have the potential to affect people far into the future and, some would argue, even future generations. 88 Thus, where effective weapons-like conventional weapons-can be contained in space and time and are not used in favor of weapons which cannot-like nuclear weapons-use of nuclear weapons would be manifestly illegal under humanitarian law. Proportionality The principle of proportionality appears in a number of places in Additional Protocol I to the Geneva Conventions. For instance, Article 51(5)(b) prohibits: "[A]n attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated." 89 Article 57(2)(a)(iii) and (b) effectively repeat this language. 90 And, according to Article 57(2)(a)(ii): Proportionality [W]ith respect to attacks, the following precautions shall be taken: those who plan or decide upon an attack shall: take all feasible precautions in the choice of means and methods of attack with a view to avoiding, and in any event to minimizing, incidental loss of civilian life, injury to civilians and damage to civilian objects. (2015); see also supra note 53. 89 Additional Protocol I, supra note 75, art. 51(5)(b). 90 Id. art. 57(2)a(iii), 57(2)(b). 91 Id. art. 57(2)(a)(ii). Proportionality In other words, an attack-even an attack that is anticipated to achieve a concrete and direct military advantage-cannot disproportionately kill or injure civilians. Rather, both the anticipated military advantage and the loss of civilian life must be calculated prior to the attack. In this sense, and as the language makes plain, there is a foreseeability criterion built into the proportionality standard. 92 Thus, like other standards, the test for proportionality considers what is reasonable under the circumstances. Proportionality As opposed to a conventional weapon attack, a strategic nuclear attack near a civilian population is exceedingly likely to be disproportionate. Conventional weapons, and especially "smart" weapons, can target discrete military objectives even within civilian populated areas. Yet when it comes to nuclear weapons, the number of civilians killed and injured will be exponentially magnified by the larger blast yield and radiation; again, with the latter inflicting death and disease throughout the lifetime of survivors of the initial blast-surely a foreseeable consequence given the experience and extensive studies done regarding the survivors of Hiroshima and Nagasaki. Consequently, there is a high probability that any nuclear attack near a civilian population would be clearly disproportionate and, hence, manifestly illegal, if a conventional weapon alternative is available to achieve the same military objectives. Again, the analogy to biological weapons is instructive: like nuclear weapons, these types of weapons cause far more harm spatially and temporally than conventional weapons, rendering them disproportionate. Indeed, biological weapons were banned for this very reason. indispensable for securing the ends of the war, and which are lawful according to the modern law and usages of war." Proportionality 96 Just war theorists call this the "necessity principle." Namely, the requirement to refuse using especially catastrophic weapons when "they are not necessary to achieve legitimate military objectives and thereby minimize collateral damages to civilians." 97 Necessity is the source of some confusion in international humanitarian law. For example, it is "often misunderstood to mean that regardless of the law, warriors can do whatever it takes to win." Proportionality 98 But in fact other jus in bello principles constrain necessity, often by way of incorporation, weaving a sort of web of interconnected laws of war designed to reduce civilian death and harm. In this connection, Jeffrey G. Lewis and Scott Sagan propose that when it comes to necessity, states should refrain from using nuclear weapons when they are not necessary to achieve legitimate military objectives, thus minimizing civilian death and suffering. 99 Because we know that nuclear weapons are quantitatively and qualitatively different from all conventional weapons, this limitation makes sense. When one considers the extensive blast power and coverage, the pervasive radioactivity, and the prolonged suffering, as well as the severe environmental harms spawned by nuclear weapons, it becomes almost impossible to conclude that they would result in less civilian harm than conventional weapons near a civilian population. Thus distinct principles of the humanitarian law of necessity (which authorizes an attack to help overcome the enemy that is not contrary to other jus in bello principles) and proportionality (which requires a proportionate attack) exhibit a synergistic relationship supporting one another to prevent civilian death and harm to the most realistic extent possible. 100 Indeed, in a famous statement by the ICJ in the Nuclear Weapons Advisory Opinion, the Court observed: "The threat or use of nuclear weapons would generally be contrary to the rules of international law applicable in armed conflict, and in particular rules of humanitarian law." 101 Critical to this reasoning was the humanitarian law of necessity. The Court explained that one of the preeminent rules requires that an "armed attack" must be "necessary," a rule that interacted with the proportionality requirement and that had been "well established in customary international law. concept of military necessity was not just whether nuclear weapons were a military necessity to knock out a certain target, but also whether "the means themselves were necessary to the target and thus permissible." 103 Hence, holistically viewed, both military necessity and the means of achieving those necessities merge into an analysis ultimately designed to reduce civilian casualties and harm. 104 A case can therefore be made that where conventional weapons would achieve the same military objective as a nuclear weapon, but with less civilian death and suffering, the nuclear strike is manifestly illegal under necessity principles. Prevention of Unnecessary Suffering and Superfluous Injury Like the principle of distinction, prevention of unnecessary suffering and superfluous injury also appears
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