For many years, the United States and some of its allies have taken the view that one state (say, one of them) may use armed force on the territory of another state (say, Pakistan or Syria), without its consent, if the territorial state is “unwilling or unable” to prevent a non-state armed group from launching armed attacks from its territory. For almost as many years, others have objected that the U.S. position fails to even address the most basic questions that any viable doctrine of self-defense must persuasively answer: what, exactly, happens to the territorial state’s right not to have armed force used on its territory and what, exactly, happens to the territorial state’s right of self-defense against an armed attack by the intervening state?
The state of the debate (such as it is) was on vivid display during an important panel discussion at this year’s annual meeting of the American Society of International Law. As elegantly described by Alex Moorehead, all sides agreed that the United Nations Charter prohibits the use of armed force by one state on the territory of another without its consent but permits individual or collective self-defense if an armed attack occurs. One side, represented by Australia and the United Kingdom, emphasizes that the text of the Charter does not say that an armed attack must be attributed to another state in order to justify defensive force on its territory. The other side, represented by Brazil, insists that only attribution of an armed attack by an armed group to the territorial state could explain why the intervening state may defend itself at the expense of the territorial state and why the territorial state must allow the intervening state to do so rather than defend its own territory and civilian population.
Simply put, why should international law permit the intervening state to prefer its own safety to that of the territorial state, but forbid the territorial state from doing so in turn? If the armed attack is not attributable to either state, then why should international law permit the intervening state to use defensive force rather than suffer armed attack? And why should international law require the territorial state to suffer armed attack rather than use defensive force? In other words, what makes the “unwilling or unable” approach consistent with the principle (discussed below) that “there can be no self-defense against self-defense”?
To date, these questions have remained mostly theoretical. For the most part, powerful states rely on the “unwilling or unable” approach when using armed force on the territory of weaker states who would be foolish to respond with armed force in turn. However, in a few cases, near-peer militaries have come dangerously close to direct confrontation, if not all-out-war.
Last year, a U.S. fighter jet shot down a Syrian warplane, leading Russia to announce that it would consider U.S. military aircraft legitimate targets in certain areas. The U.S. military claimed to act “in collective self-defense” of Syrian Democratic Forces (SDF), who were supposedly “conducting legitimate counter-ISIS operations.” For its part, Syria views the SDF as a separatist group seeking to create an autonomous Kurdish region in Syria or a Kurdish state independent from Syria. So the world briefly saw a claim of collective self-defense (by Russia, of Syria, against the United States) against collective self-defense (by the United States, of the SDF, against Syria) against individual self-defense (by Syria, against the SDF) against individual and collective self-defense (by the United States and the SDF, of the United States and Iraq, against ISIS). Thankfully, Russia and the United States reached an accommodation and avoided direct conflict.
There have been other close calls. In January, Turkish forces entered Syria, claiming self-defense against Kurdish armed groups, while Syria pledged to “defend [its] people against the Turkish aggression.” Russia and Iran interceded, the prospect of direct hostilities faded away, and the legal problem remained unaddressed.
Ideally, we should address such legal problems before they arise in practice. Otherwise, they will remain hidden, inches below the surface, ready to explode when finally stepped upon. Unfortunately, as we will see, there are reasons to fear that this particular legal problem will not be resolved until it is too late.
Self-Defense Against Self-Defense?
Let us begin with “‘traditional” interstate conflict. As the Nuremberg Military Tribunal declared in The Ministries Case,
he who initiates aggressive war loses the right to claim self-defense against those who seek to enforce [the Kellogg-Briand Pact prohibiting aggressive war]. This was merely the embodiment in international law of a long-established principle of criminal law : * “* * * there can be no self-defense against self-defense. [emphasis added]
Similarly, under the United Nations Charter, a state that carries out an armed attack against another state loses the right to claim self-defense against the victim state, its allies, or the international community acting through the Security Council (at least so long as the defensive response is necessary, proportionate, and otherwise lawful, a caveat I won’t repeat).
The explanation is not hard to find. By unlawfully attacking another state, the aggressor state forfeits its right not to have force used against it, as well as its right to defend itself from such force. In contrast, the victim state has (presumably) done nothing to forfeit its own right not to have force used against it or its right to defend itself from such force. The unlawful armed attack explains the legal asymmetry between the aggressor state and the victim state, that is, why “there can be no self-defense [by the aggressor state] against self-defense [by the victim state].”
Importantly, the same principle applies if an armed attack by a non-state armed group is attributable to the state from whose territory the group operates. According to the International Court of Justice (ICJ), such attribution requires that the territorial state exercises effective control over the armed attack, essentially carrying out the armed attack through the non-state armed group. Of course, one might argue that the ICJ’s standard of attribution is too narrow. Or one might argue that attribution is not required to explain the loss of the territorial state’s rights. However, the “unwilling or unable” approach is not presented as an attribution standard at all, nor does it provide any alternative explanation for the loss of the territorial state’s rights.
To fix ideas, consider the following scenario:
Non-state armed group G carries out armed attacks against State A from the territory of State B. State B does not control or support group G. However, State B is either unwilling or unable to use the level of military force that State A is both willing and able to use in order to prevent further armed attacks by group G. If State A does not use force in State B, then many of State A’s civilians will be killed by group G. If State A uses armed force in State B, then it will kill many of State B’s civilians.
According to the “unwilling or unable” approach, these facts alone give State A the right to use armed force against group G in self-defense. However, these facts alone do not explain why State B would lack a right not to have force used on its territory, or why State B would lack a right to defend its territory and its civilians from State A. Let me explain.
In general, an action that would ordinarily contravene a right may be justified on one of three grounds: the right may be waived by knowing and voluntary consent; the right may be forfeited by wrongdoing; or the right may be overridden to prevent a greater evil. Importantly, it is generally impermissible to use force to defend a right that has been waived, forfeited, or overridden. So, if the territorial state’s rights are waived, forfeited, or overridden, then this would explain why it may not claim “self-defense against self-defense.” Let’s examine these possibilities in turn.
First, the territorial state’s rights are not waived. The whole point of the “unwilling or unable” approach is to justify the use of armed force without the consent of the territorial state. Indeed, according to the United States, the intervening state does not need to ask for the consent of the territorial state prior to using armed force on its territory, and may reject the territorial state’s offer to consent on the condition that the intervening state agrees to coordinate military operations.
Second, the territorial state’s rights are not forfeited. The “unwilling or unable” approach does not require any unlawful action or omission by the territorial state that would explain the loss of its right against force or its right to self-defense. The territorial state may be ‘willing’ to respond to the threat posed by the armed group with law enforcement measures or negotiations but not with military force that may kill many of its own civilians, consume troops and equipment needed elsewhere, or trigger a broader internal conflict. Similarly, the territorial state may be ‘able’ to respond, but not as quickly or effectively as the intervening state, which may have greater military capability or fewer reservations about using military power to its furthest legal limits. None of these forms of unwillingness or inability to prevent further armed attacks involve any unlawful act or omission that would explain the loss of the territorial state’s rights.
Finally, the territorial state’s rights are not overridden. In principle, if attacks by the group would seriously infringe State A’s territory and kill many of State A’s citizens, while State A’s use of force would less seriously infringe State B’s territory and kill few of State B’s citizens, then State A might be justified in acting while State B might be unjustified in resisting. However, the United States has never claimed that it may use armed force against armed groups only if doing so will prevent a ‘greater evil’, judged from an impartial point of view that places equal value on the rights and interests of both states as well as on the lives and welfare of their respective citizens.
Importantly, while the United States accepts that “[a]ctions in self-defense must be proportionate,” it interprets proportionality to mean that “[f]orce can be used in self-defense, but only to the extent that it is required to repel the armed attack and to restore the security of the party attacked.” On this view, defensive force is proportionate if and only if it inflicts no greater harm than necessary to repel or prevent armed attacks. However, on this view, defensive force may be proportionate even if it inflicts more harm than the armed attacks would have inflicted.
In a typically convoluted section, the U.S. Department of Defense Law of War Manual discusses principles drawn from the Just War Tradition which may be reflected in modern law of war rules. While the just war principle of proportionality involves weighing the contemplated actions with the justification for taking action, the legal rule of proportionality remains that force may be used in self-defense to the extent required to repel the armed attack or reasonably necessary to discourage future armed attacks. In other words, the legal rule of proportionality does not require impartially weighing the harm inflicted by defensive force against the harm prevented by defensive force.
Whether U.S. action against armed groups has, in fact, inflicted more harm than it has prevented is a complex empirical question that I will leave for another day (for a related inquiry, see here). In this post, I am only concerned with the legal doctrine that the United States has introduced (or, perhaps, reintroduced) into state practice, which permits defensive force against armed groups that is necessary to prevent armed attacks whether or not it prevents a “greater evil.”
Can the “Unwilling or Unable” Approach be Fixed?
In its current form, the “unwilling or unable” approach seems untenable. Can it be salvaged? Perhaps. But I doubt it will be, because the most obvious remedies for its defect do not serve the interests of the states that endorse it.
First, one might argue that the territorial state may waive its rights through implicit consent, that is, by failing to complain about the use of force on its territory by the intervening state. This proposal obviously will not apply when the territorial state explicitly protests the actions of the intervening state. Moreover, if the territorial state is initially silent, but later asserts its rights, claiming that its initial silence was not intended as an implicit waiver, on what grounds could the intervening state object? Accordingly, I see little prospect that proponents of the unwilling or unable” approach will accept such a limitation.
Second, as suggested above, one might argue that the territorial state may forfeit its rights through unlawful acts or omissions that fall short of exercising effective control over the armed attacks by the armed group. Such unlawful acts might include general financial or military support for the armed group, while such unlawful omissions might include failing to exercise “due diligence” in preventing its armed attacks. Rather than canvass every possible version of such an argument, I’ll confine myself to some general remarks.
On one version of the argument, forfeiture requires attribution, but attribution does not require effective control. Accordingly, the territorial state’s unlawful acts of support or omissions of due diligence make the attacks by the group attributable to the territorial state, which thereby forfeits its right against force and its right to self-defense.
Would the states that endorse the “unwilling or unable” approach pursue this line of argument? Personally, I doubt it, because this line of argument would almost certainly attribute to those very states—the United States, Turkey—and their allies—Saudi Arabia, the United Arab Emirates—the unlawful acts of the armed groups that they actively support or do little to control. Indeed, the logic underlying this line of argument would seem to extend beyond the case of non-state armed groups and make the unlawful acts of one state—say, Saudi airstrikes in Yemen—attributable to other states—say, the United States—that support or fail to control it.
On a different version of the argument, attribution requires effective control, but forfeiture does not require attribution. Accordingly, the territorial state’s unlawful acts or omissions do not make the attacks by the group attributable to the territorial state, but the territorial state nevertheless forfeits its right against force and right of self-defense.
Now, if the territorial state bears substantial responsibility for the threat posed by the armed group, while the intervening state bears none, then this sharp asymmetry of responsibility might explain a sharp asymmetry of defensive rights. If one state will suffer harm—the intervening state at the hands of the armed group, or the territorial state at the hands of the intervening state—then arguably it should be the state that bears exclusive responsibility for that very situation. A similar argument—weaker, though still plausible—might be made when the territorial state bears substantially greater responsibility than the intervening state for the threat posed by the armed group.
Would the states that endorse the “unwilling or unable” approach pursue this line of argument? Again, I doubt it, because these very states bear substantial responsibility for the threats posed by the armed groups that they now seek to suppress. For example, do the United States and Iraq really want to get into an argument over whether they are more or less responsible than Syria for the threat posed by ISIS? We know what Syria will say: that ISIS arose from the U.S.-led invasion of Iraq, from our detention centers, from our failure to defeat Al Qaeda in Iraq, and from Iraq’s failure to defend its territory, weapons, and resources.
Finally, one might argue that the territorial state’s rights are overridden if the intervening state will prevent substantially more harm than it will inflict, such that its use of armed force is clearly the “lesser evil.” As Dapo Akande and Thomas Liefländer suggest, while the proportionality constraint in the law of self-defense might otherwise require only that defensive force do no more harm than necessary to repel or prevent armed attacks, in the current context proportionality may require comparing the harm done and the objective pursued. While the latter approach “requires complex value judgments,” this may involve impartially weighing the interests of both states and all potentially affected persons.
On this view, the intervening state may not defend its own citizens from the armed group if doing so will inflict greater harm on the citizens of the territorial state. Similarly, the territorial state may not defend its own citizens from the intervening state if doing so will enable the armed group to inflict greater harm on the citizens of the intervening state. Both states must place equal weight on the lives and wellbeing of all affected persons, regardless of nationality.
Would the states that endorse the “unwilling or unable” approach pursue this line of argument? Unfortunately, I doubt it. Even in the best of times, it is hard to imagine the United States government declaring that it will not prioritize the lives and safety of American citizens and, accordingly, will not defend its citizens from ISIS, al Qaeda, or other armed groups if doing so will likely result in equal or greater harm to Syrians, Pakistanis, or others. In the current political environment, in which the President of the United States pledges to put “America First” and encourages other states to put their own citizens “first,” the prospect seems especially remote.
In my view, the suggested modification of the legal rule of proportionality reflects sound moral principles and would represent a progressive development of international law. But I’m not holding my breath for its adoption by the United States, its allies, or its adversaries.
In this rather depressing essay, I’ve argued that the ‘unwilling or unable’ approach, as adopted by the United States and its allies, is something of a doctrinal embarrassment. More depressingly still, the defects of the approach will likely go uncorrected, because the amendments that might correct them do not serve the interests of the states that adopt the approach. And so these defects will continue to lie below the surface. Perhaps states will continue to step around them. Perhaps strong states will continue to use force on the territory of weaker states who could not defend themselves if they tried. Perhaps near-peer militaries will continue to defuse tensions as they arise. Or perhaps one day, some state will misstep, and the explosion will be visible for all to see.