President Obama announced in his speech on September 10 that the United States would pursue expanded military (air) strikes against the Islamic State or ISIS terrorist group in both Iraq and Syria.  Many academics have already grappled with the issue of whether the President has authority for this type of military action under domestic law, with most arguing that the President did not have authority under the Authorization to Use Military Force (AUMF) (see Deborah Pearlstein’s post on Opinio Juris and Marty Lederman’s and Jen Daskal’s posts on Just Security).  What I would like to focus on in this post is the issue of legality of the proposed military campaign under international law.

As we all know, Article 2(4) of the United Nations Charter bans states from using force against the territorial integrity and political independence of other states.  The only legally recognized exceptions to this overall ban are instances where the Security Council authorizes the use of force or where the intervenor nation alleges self-defense pursuant to article 51 of the United Nations Charter.  In this instance, if the United States intervened in Iraq and Syria against ISIS, such use of military force would not be authorized by the Security Council, because the latter has been deadlocked over any use of force in the Middle East and because Russia would likely veto any future discussions of authorization to use force in this region.  Can the United States assert self-defense? Maybe.

The United States could argue either individual or collective self-defense.  If it argues individual self-defense, the United States would have to assert that it is fighting ISIS, a terrorist group and non-state actor in an area where the relevant state authority is unable or unwilling to intervene, such as in Syria or in Iraq.  While the United States has squarely adopted the position that the “unable or unwilling” test enables it to assert an individual self-defense rationale against a terrorist non-state actor operating out of another sovereign state, international law scholars have debated the legality of this approach and have been far from reaching a consensus on this issue.  Moreover, it appears that at least Syria asserts that it is willing and able to fight ISIS; the United States’ position vis-a-vis Syria on this issue is thus complex and has been summarized in a recent excellent post by Ryan Goodman on Just Security:

“What is the international law when a host state (Syria) is willing and able to deal with a nonstate group (ISIS) through military cooperation with the threatened state (the United States) but the latter (the United States) doesn’t want to associate itself with the host state for other potentially unrelated reasons?”

Thus, it appears that the United States’ rationale for using force against ISIS in Iraq and Syria is shaky at best under international law, because of lack of consensus in the scholarly community about the “unable or unwilling” test and because of the test’s complex application  to the Syrian context (arguably, Iraq is “unable or unwilling” to fight ISIS).

Another possibility for the United States would be to argue that the recent beheadings of two American journalists by ISIS amount to an “armed attack” against the United States, within the meaning of Article 51 of the United Nations Charter.  This interpretation of Article 51 is possible although it is likely that many in the scholarly community would disagree with it.  While it appears that most scholars and some states have embraced the view that states may assert a self-defense rationale when fighting against non-state (terrorist) actors, there is no consensus on what type of attack by a non-state actor against a sovereign state could trigger the latter’s right of self-defense.  9/11 terrorist attacks against the United States constituted an “armed attack” according to most, if not all scholars, but the beheadings of two American journalists, however gruesome they may have been, may not reach the same threshold.  Thus, the armed attack argument remains subject to debate in this context.

Finally, the United States could claim collective self-defense in order to justify its use of military force against ISIS.  In order to do so, the United States would have to make the argument that the governments of Iraq and Syria invited the American intervention.  This argument is easier to make with respect to Iraq than Syria, because the former may very well agree to the presence of American forces and may thus “invite” air strikes, while it is unlikely that Syria’s President Assad would so agree or make such a request.  The collective self-defense argument works better in the Iraqi context, but is weak when it comes to Syria.

I should also point out here that  although some scholars have argued in favor of a humanitarian intervention in the context of Syria, the latest American-announced air strikes do not fall in this category because they will be directed against a terrorist group and will not be aimed at easing humanitarian suffering.   Overall, it appears that the United States government is asserting an individual self-defense argument based on the “unable or unwilling “test for both its actions in Iraq and Syria.  These actions will hopefully prove useful in the global fight against terrorist groups such as ISIS; they will certainly continue to raise difficult international law issues.