While it was only last night that the United States and five Arab nations began air strikes against ISIL and the al-Qaeda-linked Khorasan group inside Syria, Just Security has been exploring the legality of such strikes for nearly a month. Much of the debate is framed around the question: when is the U.S. justified in conducting military strikes inside a sovereign country without its consent?

Below is a quick recap.

On Aug. 28, Just Security’s Co-Editor-in-Chief, Ryan Goodman kicked off what turned into an excellent debate on the site by asking whether the Syrian government is “unwilling or unable” to deal with the security threats posed by ISIL and other terrorist groups on its territory, thereby meeting what appears to be the U.S. criteria for conducting air strikes inside Syria.

[D]oes 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 Syria 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.


“A state that is unable or unwilling to effectively police its territory should not be given the right to direct the actions of an intervening state.”

On Sept. 12, Michael Lewis responded to Ryan’s post by arguing that even if the Syrian government is willing to fight ISIL within its borders, the U.S. is justified in using force against ISIL inside Syria because Damascus has proven to be unable to do so effectively. (Click here for Goodman’s response to Lewis.)

Below is the meat of Lewis’ claim:

States have an obligation to prevent their territory from being used as a base for launching attacks on other states. If they are either unable or unwilling to prevent such attacks from being planned, prepared and executed from their territory then states that are impacted by those attacks have a right to take measures to prevent the territory from being so used. In this case Syria is unable to prevent its territory from being used by ISIS to plan, prepare and execute attacks against targets in Iraq (and depending upon who you believe, in the US as well). Whether they are willing to cooperate with the US strikes against ISIS is irrelevant to this analysis.

This strikes me as being the better position from a policy standpoint as well. A state that is unable or unwilling to effectively police its territory should not be given the right to direct the actions of an intervening state.


“Michael’s proposed solution—while no doubt intended to be in the interest of U.S. security—would open a Pandora’s box, be it now or later, for the United States, its allies, and many others.”

Lewis’ interpretation of the unwilling or unable argument “makes war more permissible than what international law intended,” wrote Jonathan Horowitz in a Sept. 12  response to Lewis’ piece. Horowitz argues that basing decisions to use military force to eliminate threats on the ability, or inability, of states to exert control over their territory opens the door to a “forever war” by the U.S.

If the United States thinks it can suppress the threat of ISIS in a territory that it does not control, why should Syria’s inability to control that same territory necessarily mean that it too could not suppress the same threat? And, if Syria could suppress the same threat without territorial control, then why should Syria lose its sovereign rights? Michael’s logic simply doesn’t work for me. I’ll concede that my questions might get a bit more hairy if we talk about detention operations, instead of airstrikes, as a means of suppressing a threat. In detention operations territorial control may (may) be a more determining factor. But the fact that different scenarios alter the terms of the unwilling/unable test goes to my main point: What is needed is a fact-based test that considers both the threat and Syria’s ability to deal with the threat, not a generalized rule that hinges on territorial control.

I also find it difficult to accept Michael’s interpretation of the “unwilling/unable” standard—a standard which Ryan correctly notes is “a fairly well settled part of the US government’s legal position [but] remains controversial under international law”—because a state’s unwillingness or inability to act is not fixed or etched in stone, especially when that state becomes informed that its unwillingness/inability may result in heavy diplomatic consequences or, at the extreme end of the spectrum, a foreign power attacking its territory. One day a state may say it is unable or unwilling to act, but the next day may be different. This could be due to competing internal versus external politics, or the availability of resources. My point is that things can change. What Michael offers, however, seems to be too static and is effectively an end-run around the “unwilling/unable” test rather than approaching it as a complex and dynamic standard that has the function of ensuring that a state is appropriately balancing its national interests with the sovereignty of other states.

If you think of all the places in the world where states don’t have control over parts of their territory, you can quickly start to see how Michael’s understanding of the “unwilling/unable” test threatens to unravel the principle of sovereignty. Such breaches of sovereignty would be nearly always justifiable, if not encouraged. It’s also important to ask: Would the territorial states simply stand by without a response, violent or otherwise? Michael’s proposed solution—while no doubt intended to be in the interest of U.S. security—would open a Pandora’s box, be it now or later, for the United States, its allies, and many others.

Click here for Lewis’ response to Horowitz, where he argues that “willingness to act against ISIS without the capacity to do so is of little value to neighboring states (in this case Iraq) threatened by ISIS. Yet that is the standard that Jonathan advances, a standard that adds nothing to the security to states that are threatened from the ungoverned spaces of the world.”


“We should ‘re-contain’ ISIL by using military force to stop it from metastasizing.”

In a similar vein of avoiding a “forever war,” Just Security’s Harold Koh made several recommendations in Politico Magazine on Aug. 29 for how U.S. President Barack Obama should approach combating ISIL in Syria.

Namely, that the White House must seek out congressional authorization for military action against ISIL in Syria and that it should approach any fight against ISIL as a narrow action with the goal of “containing” the group to territory inside Syria.

Koh’s key recommendations were:

  • “President Obama can hardly extend a conflict with ISIL to Syria based on claims of inherent constitutional authority, when he rightly criticized the Bush administration for pursuing a ‘Global War on Terror’ based on similar sweeping claims.”
  • “To secure a domestic legal ground for action, the administration should engage with Congress to develop an ISIL-specific AUMF.”
  • “We should ‘re-contain’ ISIL by using military force to stop it from metastasizing and ‘shrink ISIL back into ISIS’ as a smaller, less ambitious non-state actor that limits its aspirations and activities to Syrian territory.”