In this essay, I make the case for armed intervention to destroy the group that calls itself the Islamic State of Iraq and Syria (ISIS). The central burden of the article is to establish the moral case for intervention.
Some preliminary concepts are in order. Wars can be classified into at least three types. A war of national self-defense is military force to defend one's state and one's compatriots from external aggression. Influential writers such as Michael Walzer claim that only the response to international aggression against a state is just (2006, 58). But this view is misleading. All attacks are against persons. An aggression against the state is an aggression against the citizens of the state. As Walzer himself says, the crime of aggression is that it forces persons to abandon their life projects and fight for survival (2006, 28). But if this is so, then any attack against persons forces them to fight for survival and justifies defensive force. The state is simply an institution created by individuals to serve human ends. A state is no more than the individuals who inhabit its territory and who created the institutions of government (Lomasky and Teson 2015, 218). When state A attacks state B, it attacks the persons in state B, thus forcing them to fight to defend their lives, liberty, and possessions. A war of self-defense is a military response to a war of aggression. But a war would be aggressive and criminal even if it were not directed at any state, but at persons living, say, in the state of nature, each one occupying his or her own land. The fact that in the real world those who fight are uniformed soldiers is irrelevant to the moral justification of self-defense and to the moral condemnation of aggression. National self-defense is individual self-defense writ large.
A war of collective self-defense is military force to defend the citizens of another state from aggression by a third state. (1) Suppose state A unjustly attacks state B. State B, unable to resist, requests help from its ally, state C. State C is justified in waging a defensive war against state A. Here again, states must be disaggregated. The army of state C uses justified military force against the army of state A, which attacked the citizens of state B and forced them to fight for their lives and property. Collective self-defense, like national self-defense, is a case of justified force in defense of others. In national self-defense, each citizen fights to defend himself and his compatriots. In collective self-defense, citizens of foreign states (usually organized in armies) help the citizens of the state victim of aggression by resisting with military force.
A humanitarian intervention is a war to defend persons from attacks in their territory by their own government or other groups. When state A invades state B and commits atrocities against civilians there, then the action by third party C to save B's victims is at the same time collective self-defense and humanitarian intervention. The focus of humanitarian intervention is precisely that: humanitarian. It is armed action to rescue people from genocide, crimes against humanity, war crimes, and other severe forms of tyranny and oppression (Teson 2005b).
The important point here is that all three forms of war are justified by a single rationale: the defense of persons. In national self-defense, the defenders act for themselves and for their compatriots. In collective self-defense, the defenders act on behalf of foreigners who are attacked. In humanitarian intervention, the interveners act to rescue victims of (usually governmental) atrocities.
The three types of war--national self-defense, collective self-defense, and humanitarian intervention--instantiate the traditional requirement of a just cause to meet the standard of jus ad helium. The just cause in all three types of war is essentially the same: the defense of persons whose lives and possessions are threatened by the aggressor. The dichotomy between national self-defense as a defensive war (and presumptively justified for that reason) and humanitarian intervention as an offensive war (and presumptively unjustified for that reason) is untenable. Both wars in self-defense and wars in defense of others (humanitarian intervention) are wars in defense of persons. Only defense of persons qualifies as a just cause; war is never justified for economic gain, national glory, reputation, and similar incarnations of the national interest.
A war against ISIS has a just cause under all three kinds of just war: national self-defense, collective self-defense, and humanitarian intervention. ISIS has directed or inspired attacks against France, Belgium, the United States, Turkey, Egypt, Yemen, Tunisia, Indonesia, and others. (2) ISIS has ordered armed attacks in the territories of France and Belgium, thus triggering the right of the French and Belgian governments to react in self-defense. It has invaded Iraq and Syria, thus triggering the right of national self-defense by those states (although the case of Syria has important qualifications), and it has committed terrible crimes against persons under its rule. I start with the most widely accepted rationale: collective self-defense.
Because ISIS has mounted massive military attacks against Iraq and Syria, third parties such as the United States are entitled to assist the victims of those attacks. Iraq has requested help and authorized the use of military force in its territory. The case of Syria is more complex, but there, too, the Syrian government has apparently authorized Russian troops in its territory (Birnbaum 2016).
With respect to Iraq, ISIS can be defined as a rebel belligerent group. As such, ISIS has risen against the government of Iraq. It is not difficult to see that in this civil war ISIS does not have a just cause. ISIS is avowedly devoted to establishing a hardline Islamic caliphate in the Middle East (Condon 2014). Whether it has global ambitions to attack the West is uncertain, but the intensity of its terrorist actions outside the Middle East suggests a positive answer. At the very least, ISIS's goal is to establish a tyrannical Islamic state. This is exactly the opposite of a just cause. The government of Iraq, therefore, is justified to resist ISIS, and third parties are justified in providing assistance to the government of Iraq. The current air strikes conducted by the United States and others are, then, justified, although, as I explain later, they are insufficient to secure victory.
ISIS has also occupied parts of Syria. May the Syrian government then legitimately request assistance against ISIS? This is problematic because, unlike the elected Iraqi government, the unelected Syrian government has rendered itself guilty of serious war crimes in the course of the civil war in that country. (3) Indeed, these atrocities started long before the civil war began. This is one of those cases where we can say that neither of the parties has a just cause. ISIS aims to topple the Syrian government, and the Syrian government is itself illegitimate. But ISIS seeks to replace the al-Assad regime with an even worse regime, and, for all we can tell, ISIS's atrocities are likely to eclipse Bashar al-Assad's, bad as the latter are. Helping the Syrian government fight ISIS, therefore, is justified, independently of whether the victors would have a further obligation to deal with the al-Assad regime later--even eventually remove him from power.
In the wake of the attacks in Paris in early November 2015, President Francois Hollande declared that France was at war with ISIS (Mullen and Haddad 2015). The question then arises: Do these attacks justify a French military response to ISIS, quite apart from France's right to help Iraq in its war against ISIS? Here we must draw a careful distinction. I think the French government is entitled to respond militarily to ISIS in the territory that ISIS occupies in Syria and Iraq. The concept of self-defense has evolved, in law and morality, to allow an armed response against nonstate actors in these cases. ISIS's attacks in Paris exceed the boundaries of common criminality and entitle France to conduct military operations against ISIS, to take the war to ISIS in the Middle East. However, France may not treat French territory as a battlefield and use the war tools to identify and kill members of ISIS in its territory as if they simply were enemy combatants (Teson 2012, 423). France, a liberal democracy, must resort to police tools consistent with human rights and the rule of law that French institutions honor. French military action in Syria and Iraq, then, is justified both as collective self-defense (assisting Iraq against ISIS's onslaught) and as national self-defense (responding to ISIS for the Paris attacks).
The case of the United States is different, however. The June 12, 2016 attack in Orlando, FL was carried out by a man who swore allegiance to ISIS (Ellis et al. 2016), and the December 2015 San Bernardino attackers were inspired by ISIS. However, both the San Bernardino and Orlando attackers appear to have acted independently of ISIS and not to have been legitimate ISIS agents. If ISIS had been behind either attack, then the United States would have had a right not only to use military force in collective self-defense to assist Iraq because ISIS attacked Iraq but also to invade Iraq as an exercise of its own right to national self-defense. Within U.S. territory, however, the United States is entitled to use police tools, not war tools, to confront the crimes committed in San Bernardino and Orlando.
The question is not moot. If the United States is acting only in collective self-defense to assist Iraq and not on its own behalf, the Iraqi government may revoke its request for assistance and ask the United States to leave. If instead the United States is acting by its own right, the...