What’s Wrong With Pre-emptive War?
It would be hard to overstate the
importance of the present debate about the legitimacy of the Iraq War and of
the legitimacy of the pre-emptive use of force in general. In this essay I will address only one aspect
of this debate, the legitimacy of the principle of pre-emptive war,
rather than the separate issue of its application to the case of
In order to investigate the question of pre-emptive war, we must first set out the nature of the right to self-defense under international law. It is beyond controversy that a nation has a right to defend itself when attacked, both under traditional Just War Doctrine and under the United Nations Charter (which calls it an ‘inherent right,’ i.e. presumably a natural right). There is however some controversy over the precise scope of the right to self-defense under Article 51 of the Charter. Does the right extend only to defense against an actual attack, as the Charter says, or is it implied that the right extends also to use invoke the self-defense right pre-emptively, where a threat is imminent but not yet actualized? A small minority of commentators argue that Article 51authorizes self-defense only against an actual attack – i.e. only after an attack has commenced. These are often called the “restrictionists”: for them it “would be unlawful to engage in any kind of preemptive actions” (id. p. 92). The rationale for the restrictive reading is that allowing nations to use force against imminent threats would open up too large a loophole for rogue nations. But limiting the use of force to actual attacks would impose a bright-line rule that would be hard to get around. Anyone can claim a threat is imminent, but there is usually clear evidence of an actual attack.
However, the restrictionist position has garnered little support. By far the dominant interpretation of international law has been that a nation is not required to wait until an actual attack, but may take steps to pre-emptively defend itself – so long as the attack is imminent. That is to say that pre-emptive self-defense is clearly permissible under international law, as part of the “inherent” right of self-defense. Whatever the actual intentions of the drafters of Article 51, it seems to be clearly the case that customary practice has made pre-emptive self-defense a fixed element in the current international law regime. There is, therefore, no substantial controversy over a nation’s right to pre-emptive self-defense against an imminent threat.
However, much of the confusion arises because the word ‘pre-emptive’ is sometimes used to mean the use of force against an imminent threat, and sometimes to mean the use of force where a threat is not even imminent. The problem seems to be a lack of agreement on the definition of key terms. Thus Mary Ellen O’Connor uses “preemptive” to mean the lack of imminence, i.e. what is more commonly called “preventive,” so for her pre-emptive force is illegitimate. She appears to use “anticipatory” to mean force against an imminent threat. Yoram Dinstein, in contrast, uses all three terms (pre-emptive, preventive, anticipatory) interchangeably as examples of impermissible use of force, but adopts the term “interceptive” to describe force that is legitimate. For Christine Gray, ‘anticipatory’ is but another name for ‘preemptive.’ Mary Ellen O’Connell prefers the term ‘incipience’ as a substitute for arguments over pre-emption and prevention; Dinstein uses this “incipience” terminology as synonymous with “interceptive” (173), i.e. as permitting self-defense against what is usually called an imminent threat.
However, whatever the terminology one prefers, the questions at stake are relatively clear. First, does Article 51 materially change the scope of the traditional or ‘inherent’ right of national self-defense; and second, how far does that traditional right extend to the use of force to pre-empt an attack before it occurs? As we have seen, the wide consensus as to the first question is that the traditional right of self-defense remains even under Article 51. On the second question, again we seem to have a general consensus that a nation may use defensive force to pre-empt harm, so long as the attack is clearly imminent (even Dinstein allows for pre-emptive force in this sense, though he would reject the term ‘pre-emptive’). Thus what is ruled out is the use of purported self-defense as a justification for the use of force against a mere potential threat, where there is as yet no attack or even imminent attack.
To state this position more simply: under both contemporary practice and tradition, pre-emptive self-defense (self-defense against an imminent or actual attack) is permissible, whereas “preventive self-defense” – where there is not even an imminent threat -- is not permissible. It is thus the imminence requirement that is crucial in this debate, and that has been in place since Daniel Webster’s famous declaration in regards to the Caroline case that self-defense is permissible only if one is threatened by an immediate and overwhelming necessity, where there is ‘no moment for deliberation’. While Dinstein has called Webster’s formula ‘hyperbolic’ (212), still he agrees that the Caroline standard remains the criterion for self-defense by states (219). If the attack is not imminent, however, but merely a future possibility, then self-defense is not legitimate. It is then nothing radical at all to defend the right to use pre-emptive force. It is, however, a major shift to claim that a nation may resort to preventive self-defense, where there is not even an imminent threat as yet. And this, it is widely agreed, is not permissible.
Indeed, it may be said that the very idea of “preventive self-defense” is in fact oxymoronic and incoherent. Self-defense, it has been argued, is inherently pre-emptive; it is meant to head off harm before it occurs. Thus the very purpose of defensive force is to ward off an attack: that is what renders it ‘defensive.’ In contrast, the use of force to prevent possible future threats is no longer defensive in the strict sense, but offensive. That is to say, it is no longer ‘defensive’ in nature. For the very idea of self-defense intrinsically involves action aimed at removing or pre-empting an immediate threat. As Suzanne Uniacke explain, self-defense is justified only against an immediate attack based on the “requirement of defensiveness: force is used in self-defence if it resists, repels, or wards off an immediate threat.” Kimberly Ferzan similarly defends the imminence requirement for both personal and national self-defense as the “defining aspect of self-defense: that self-defense is an action against a threat.” To argue for a new right of “preventive self-defense”, one that does away with the imminence requirement, does violence to the very concept of self-defense. Thus if the defenders of pre-emptive war mean by that a right to preventive self-defense, even before an attack becomes imminent, it is safe to say the argument must fail. There is no such thing as preventive self-defense.
However, this does not end the debate, for it is possible that this is not what the defenders of preventive war are suggesting. Two other possibilities suggest themselves. First, it is possible that the argument is not to eliminate the imminence requirement, but rather to revise and broaden it, thus permitting a form of self-defense that satisfies a more flexible interpretation of ‘imminence.’ A second possibility is that the argument for pre-emptive war is rather a claim for the legitimacy of the use of force that goes beyond mere self-defense. This latter possibility will be treated in the next section. Here we consider the position of the Revisionists.
It is widely noted that the concept of ‘imminence’ cannot be as strictly applied to nations as to individuals. As Dinstein explains, a “State under attack cannot be expected to shift gear from peace to war instantaneously” (212), given the need for collective coordinated decisionmaking, mass mobilization, and so forth. To apply the Caroline standard literally – self-defense is justified only if there is “no moment for deliberation” -- would prevent any meaningful response by states, nor is it a standard we really want to apply (we want states to deliberate before striking out). This does not mean however, as some critics have argued, that the Caroline standard is not a genuine part of international law, or that it should be jettisoned. Quite the opposite: it has attained, as John Yoo recognizes, ‘mythic status’ as a foundational element in international law. It is just that Webster’s statement should be taken, as Dinstein suggests, as hyperbolic but nonetheless accurate insofar as it insists that immediacy is a primary requirement of self-defense.
Of course, the difficult with implicitly or explicitly rejecting the Caroline standard is twofold: first, it requires a radical rewriting of the international law of self-defense. Even more serious, if the Revisionist position turns out to be a way not of merely tinkering with the Imminence Requirement, but rather jettisoning it, then it is subject to the objection of incoherence: it can no longer be justified as defensive force, but is in need of some wholly new moral and legal basis. Note that this issue is not merely one of technical conformity with the law of self-defense, much less a merely conceptual issue about the ‘meaning’ of self-defense. It is a deeply moral question about the legitimacy of the use of force. The most universally recognized justification for the use of force in international law is that it is defensive. One ought to be quite wary of giving up this justification without serious attention to what the alternative will be.
It is of course possible to develop a genuine Revisionist account of the imminence requirement. As we have seen, it is widely accepted that the imminence requirement should be interpreted less strictly with regards to nations than with regard to individuals. Even more important, it seems equally uncontroversial that imminence is relative to circumstances, including both the nature of the threat and the capacity to defend against it (e.g. the nature of the delivery system, the detectability of the attack, the ability to take defensive measures against it). In the days when an attack required an actual cross-border invasion by a massive force, there would have been much more warning and therefore a much stricter standard of imminence. But when the threat is a nuclear weapon smuggled into the country inside a suitcase to be detonated by surreptitious terrorist agents, a judgment of imminence should be interpreted far more loosely. It is crucial, however, to retain the distinction between revising the imminence standard and getting rid of it altogether.
Not surprisingly, the very same ambiguity about the concept of imminence appears in the “Bush Doctrine” and its justification for pre-emptive force in the 2002 National Security Strategy document and elsewhere. The NSS argues explicitly for the traditional right of “pre-emptive” self-defense rather than preventive force:
As we have seen, the crucial
question is whether the imminence requirement is maintained. Here we get conflicting signals. In an interview on Meet the Press (
We must adapt the concept of imminent threat to the capabilities and objectives of today’s adversaries. Rogue states and terrorists do not seek to attack us using conventional means. They know such attacks would fail. Instead, they rely on acts of terror and, potentially, the use of weapons of mass destruction – weapons that can easily be concealed, delivered covertly, and used without warning.
both White House Press Secretaries (Fleischer, McClellan) at different times
indeed claimed that
The question is crucial, for as I have argued, pre-emptive self-defense is a legitimate concept under traditional Just War Doctrine and current international law. But preventive self-defense – where there is no imminent threat – is not legitimate, or even coherent. And this is not, as President Bush suggested to Tim Russert, a mere matter of ‘word contests,’ but rather a crucial substantive question of law and morality. However, as we shall see in the next section, to rule out the idea of ‘preventive self-defense’ is not to reject the idea of preventive force even where there is no imminent threat.
I have suggested that the very idea of preventive self-defense is extremely dubious morally and legally, indeed arguably oxymoronic. However, even if this is correct, that does not end the debate, for there is another closely related issue that is easily confused with the first. That is: while preventive self-defense is not a legitimate concept in the Just War tradition, the same does not hold for preventive force more generally. In the domestic case, self-defense is properly understood as an exception carved out from the “monopoly of force” that society holds. In general the citizen is not permitted too resort to force, as that is the province of the police. But where the individual is under an immediate threat, such that he cannot resort to society to protect him in time, he is permitted to use self-defense. Thus we see the origin of the imminence requirement: if the threat is not imminent, then the individual does not have an excuse for violating the societal monopoly on force. A citizen’s use of force is thus limited to self-defense precisely because of the societal monopoly on force. It does not, however, follow that society itself is limited to defensive force. Quite the opposite: the police power extends beyond the imminence requirement in both directions; society is entitled to punish past wrongdoings as well as prevent future harms.
The analogy at the international level holds: while signatories to the United Nations Charter cede the monopoly on the use of force to the Security Council, they explicitly reserve the ‘inherent’ right to act in self-defense, where there is an immediate threat. But it does not follow, of course, that the Security Council itself is limited to defensive action against imminent threats. For self-defense is only one form of the use of force. The United Nations itself may use force in ways that individual nations may not – and among these is the preventive use of force. Indeed, the UN Charter explicitly states as one of the purposes of the United Nations the “prevention and removal of threats to the peace” (Article 1; cf. Art. 2(5), Art. 50). Indeed, it is widely and plausibly assumed that, whatever the legitimacy of the United States’ decision to declare war on Iraq, the United Nations would have been within its rights to authorize just such preventive force against Iraq if it so decided, regardless of whether Iraq posed an ‘imminent’ threat.
about before the establishment of the United Nations regime? Were nations permitted to use preventive as
well as pre-emptive force under Just War Doctrine? It is one of the great contemporary fallacies
about the Just War Doctrine that the only traditional just cause for war is
self-defense. Paul Ramsey labels this
misconception the modern Aggressor-Defender model of war, under which the
initiation of force is prohibited, and preventive war is “wholly unjustifiable
under any circumstance.” In fact, this model reflects not the Just
War tradition but the 20th century ideal of limited war, as reflected in the
Kellogg-Briand Pact and the
is clear that both tradition and contemporary international law do indeed
permit the waging of preventive war, so long as it satisfies all other Just War
principles and principles of law.
Indeed, it would be exceedingly odd to insist that there is a universal
moral duty not to prevent harm before it happens – especially since, as Grotius
recognized, we grant the right to prevent harm in the domestic context. Further, there seem to be some clear
historical examples where in retrospect preventive war would have been a good
idea. The most commonly cited example is
Nazi Germany’s illegal remilitarization of the
serious concern about preventive war, however, is the great danger of its
misuse. One of the motivations for the
Aggressor-Defender Model was that it limited the justification for war to clear
cases of invasion or aggression, where there is no doubt about the need for the
use of force. In contrast, where there
is a potential future threat, even the most well-intentioned decisionmakers
will have great trouble assessing whether there is a sufficient future threat
to justify war. And of course not every
decisionmaker is so well-intentioned, and can easily claim some future
potential threat as a justification for his aggression.
However, even granting the seriousness of these concerns, it is important to recognize that the concerns expressed here are about the misuse of preventive force, and do not constitute rejections of preventive force itself. The real concern, of course, is that the more force is preventive rather than defensive (i.e. aimed at preventing potential future harm rather than actual present harm), the more it risks turning into its opposite: aggression against the innocent. These concerns call for the need for clear evidence of a genuine threat before justifying resort to force. The problem is a familiar one in the domestic context as well. We want police to proactively intervene to prevent crimes before they occur, thus we create categories of crime such as ‘attempt’ and ‘conspiracy’, which allow arrest and prosecution even where the underlying substantive crime was not committed. Yet at the same time, we express concern for the rights of the accused, since we cannot always be sure they whether they might have decided not to commit the crime after all (hence we distinguish a genuine attempt from ‘mere preparation’, which is not criminal). In domestic law enforcement, as in international law, we must struggle to find a balance: intervene too early, and we risk harming the innocent; intervene too late, and the harm is already done. But it must be insisted that, whatever the risks, the use of preventive force is and should continue to be a legitimate tool in both the domestic and the international context. Still, we must recognize the crucial restrictions on its use, including most significantly the ‘proper authority’ requirement of Just War Doctrine.
We have argued that preventive force is a legitimate just cause both in Just War Doctrine and under the United Nations regime, of course subject to the other restrictions such as necessity and proportionality. But most important is the requirement that the use of preventive force is restricted to the proper authority. We need not delve into the complex question of who counted as a proper authority in Just War tradition, as the question is clearly settled by the United Nations Charter: only the Security Council has the authority to approve of the preventive use of force. Nations acting individually or collectively have only just cause for the use of force: self-defense against an imminent threat: and of course the only reason for the exception is that where the threat is not imminent, there is no opportunity to go to the Security Council for protection. This is of course a direct analogy to the domestic context, where the state has a monopoly on all uses of force besides self-defense, and preventive force is not allowed to individuals or groups.
One might see this idea of a monopoly of force as a response to the problem of abuse and manipulation of preventive force. To allow individuals to decide when there is a sufficient potential threat that requires preventive action now is to invite abuse. For it violates the fundamental principle of law that no one should be a judge in his own case.
Even the most well-intentioned actor will be prone to exaggerate the danger of future harm and the need for current action, as well as to judge his opponent’s conduct more harshly and his own conduct more generously. The public authority provides an objective, disinterested viewpoint with which to judge the necessity of force. Only where the attack is imminent do we permit an exception to this, for at least there is a bright line by which to judge the legitimacy of the resort to force. Indeed, the Charter requires that a nation exercising its right of self-defense immediately refer the matter to the Security Council for judgment as to the legitimacy of the resort to force.
It might seem then that the issue is settled: preventive force is not available to anyone other than the Security Council. However, there is yet another level of debate to be found here: whether the restrictions in the Charter are still valid and binding. We might call this the Unilateralist Argument. On this view, the limitation to self-defense under the U.N. Charter is predicated on the Security Council in fact being effective at protecting individual nations; no country would rationally cede its right to preventive force unless it had the assurance that it would be in its interest to do so. But if the Security Council proves to be unable or unwilling to use preventive force where necessary to protect an individual country, that country retains (or regains) its right to the broader use of force on its own. This in fact seems to be just the position of the NSS:
We will disrupt and destroy terrorist organizations
by …defending the
Thus although this passage uses the language of pre-emption and self-defense, its underlying meaning seems to be rather one of preventive force (“identifying and destroying the threat before it reaches out borders”; “prevent them from doing harm”).
Where the international authority has failed to carry out its mandate of the use of preventive and punitive force, the right reverts to individual nations to do what is necessary to protect themselves.
Critics of this outlook, of course, argue that
it is blatantly self-serving and a self-fulfilling prophecy as well. Every nation will be liberated to act on what
it deems is its best interests, and the very idea of the international rule of
law will disappear. And the nature of
unilateral action raises the problem of judging one’s own cause – as for
instance where the Bush Administration was able to see clear evidence of WMD’s
My purpose in this essay is not to evaluate any of these arguments, adjudicating as to the status of the United Nations, or the legitimacy of unilateral action. Rather, the aim here is simply to articulate the various strands in the debate over the use of preventive force, for it is an unfortunate feature of the argument that these distinct strands are continually getting tangled together. The lack of standardized terminology is part of the problem: there is no clear distinction between preventive and preventive, or between defensive force and force more generally. But, I have tried to argue, the inconsistency in terminology reflects much deeper ideological divisions in law and morality over the legitimacy of force. In order to sort these out, we need to demand that opponents or proponents of ‘pre-emptive war’ identify just what their position is.
Hence, as we have seen, the National Security Strategy is multiply ambiguous on the key issues. Is it arguing for an expanded right of self-defense, or for a right to unilateral preventive force? Is it arguing for ‘adapting’ the imminence requirement as it claims, or is this an indirect way of rejecting imminence? Is it suggesting the United Nations does not have a monopoly on preventive force at present? The document is particularly (no doubt deliberately) ambiguous as to its view of the United Nations.
While it offers no direct criticism of UN, it gives no particular praise of it either, and the few times it is mentioned at all it is grouped together with other international organizations: thus the United States “is committed to lasting institutions like the United Nations, the World Trade Organization, the Organization of American States, and NATO as well as other longstanding alliances.” Furthermore, the document insists on a right to unilateral action: “we will not hesitate to act alone.”
However valuable such ambiguity may be from a political or legal perspective, it is the job of the scholar to insist on clarifying as far as possible the moral and legal basis for pre-emptive/preventive war. My aim in this essay is to engage in just such a clarification of the debate, though without attempting to resolve the issue either in general or specifically with respect to the Iraq War. Nonetheless we can state the key findings thus far:
1) the idea of ‘preventive self-defense’ where there is no imminent threat is incoherent and confused;
2) Imminence is an absolute requirement for a claim of self-defense, though there is an argument to be made that the imminence standard needs to be interpreted less strictly in regards to international conflicts, especially where there are weapons of mass destruction;
3) Contrary to the received wisdom, there is nothing intrinsically wrong with preventive war (or the preventive use of force more generally), though of course it is subject to important constraints (proportionality, necessity, etc.);
4) A crucial restriction on the use of preventive force is the Public Authority requirement. Under the U.N. Charter, the only body entitled to authorize preventive international force is the Security Council.
The current debate over pre-emptive war is thus, it seems, largely misguided. The central issue is not the legitimacy of pre-emptive war per se, but rather the status of the international law regime in place since the founding of the United Nations. Has the Security Council failed in its responsibility to exercise its authority to prevent threats to the peace? And if it has, are individual nations now permitted to take over that function, and protect themselves with pre-emptive use of force even where there is no imminent threat? The heart of the debate, it seems to me, is not the question of the legitimacy of pre-emptive/preventive force, but rather the question of the unilateral use of preventive force by nations acting without authorization from the Security Council.
Anthony Arend, “International Law and the Preemptive Use of Military Force,”
 “The Myth of Preemptive Self-Defense”
 War, Aggression and Self-Defence
 International Law and the Use of Force, p. 111 ff.
 see e.g. Walzer p. 74-75; David Rodin, War and Self-Defense, p. 113.
 Uniacke, Justifiable Homicide, p. 165.
 Defending Imminence p. 252. See also Dinstein p.183-4, describing the 3 conditions of self-defense as necessity, proportionality, and immediacy.
See, e.g., G.
 Ramsey, The Just War p. 61-69
Maggie Lawson, “The Fatal Legend of Preemptive War,” National Catholic