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International Law on Airstrikes against ISIS in Syria

The administration is actively considering the option of using military force against ISIS in Syria. As the New York Times editorial board states today: “The United States, however, has not been invited into Syria, and the Obama administration has not articulated a legal justification for crossing the border.”

So what might be the justification under international law?

[Colum Lynch has a very good piece in Foreign Policy, which canvases experts on this very question and in which I am quoted. This post provides a further elaboration of my opinion on the international legal framework.]

In conducting attacks against ISIS, the United States might assert either (1) the right of individual self-defense due to ISIS’s direct threat to the United States; or (2) the right of collective self-defense in coming to the aid of Iraq. At this point, the former is a weak one—without a truly imminent or actual “armed attack” against the United States. The latter is solid.

But what about US forces crossing the border into Syria? The US government would likely assert that Syria is “unwilling or unable” to deal effectively with the ISIS threat. This is the same prerogative that the United States invokes in other parts of the world (think: the US operation to kill Osama bin Laden without seeking Pakistan’s approval). The “unwilling or unable” test is now a fairly well settled part of the US government’s legal position. Nevertheless, it remains controversial under international law.

In a post back in February, I referred to some of the active debates among international legal scholars on this question of international law:

“Can the United States send armed forces into another state to deal with a national security threat from a militant group when the host state is “unwilling or unable” to contain the threat? That question has been a focus of debates among international legal experts including Daniel BethlehemAshley DeeksKevin Jon HellerChristian Tams (plus many others in the American Journal of Int’l Law in April 2013 and July 2013).”

There are potentially two additional complications for airstrikes in Syria.

First, a strong case could be made that the US prerogative to strike in Syria would be conditioned on Iraq’s request for assistance including Iraq’s determination with respect to Syria. That is, if the United States were to conduct operations against ISIS in Syria on the basis of collective self-defense of Iraq, the government of Iraq would presumably need to request the US take the fight to Syria. Iraq may thus also need to accept the doctrine of unwilling or unable and determine that Syria fails the test.

Second, does Syria present a case of a state that is “willing and able”? Assad has demonstrated that he is utterly unwilling or unable to deal with the ISIS threat effectively. But, the Syrian government has now essentially stated that it is willing and able to cooperate with the United States in carrying out strikes against ISIS. And the Syrian government has said, “Any strike which is not coordinated with the government will be considered as aggression.”

In a statement that is a bit stunning when viewed in light of international law, the State Department spokesperson said earlier this week, “We’re not looking for the approval of the Syrian regime.”

Therein lies the complication: 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?

The “unwilling or unable” test is already a (controversial) exception to international law’s cardinal prohibition on the use of force in another state’s territory. It would be hard, to say the least, to suggest there is an additional “exception to the exception.” Given the importance of the use of force prohibition in international law and politics, it is also difficult to read the exception broadly.

I suppose the US government will have to argue that Assad is not truly willing or able even in these circumstances. First, the United States could argue that Assad is not acting in good faith. Indeed, many close observers believe Assad is playing a double game in which he has deliberately failed to quell ISIS in order to try rally parts of the international community to his side. Second, the United States might argue (like here) that the involvement of Syrian military and intelligence would compromise the effectiveness of the operations to the point that the operations would not be able to deal effectively with the ISIS threat. On that front, some close observers think the opposite is true (that the US needs Syrian support for more effective operations).

There may be other ways to address these legal complications. My point here is to explain the legal framework in which the administration may need to operate.

[For additional analysis, see Ashley Deeks’s post over at Lawfare.]

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About the Author

is co-editor-in-chief of Just Security. Ryan is the Anne and Joel Ehrenkranz Professor of Law at New York University School of Law. He served as Special Counsel to the General Counsel of the Department of Defense (20015-16). You can follow him on Twitter (@rgoodlaw).