Foreign Relations & International Law

Chemical Weapons in Syria: Enough to Justify the Use of Force?

Ashley Deeks
Friday, April 26, 2013, 10:25 PM
Now that the United States has acknowledged – with a modest level of confidence – that the Syrian government has used chemical weapons against the rebels, many press articles are asking whether (or arguing that) the United States should consider using force in Syria.

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Now that the United States has acknowledged – with a modest level of confidence – that the Syrian government has used chemical weapons against the rebels, many press articles are asking whether (or arguing that) the United States should consider using force in Syria. See, for example, here, here, and here. Senators McCain and Feinstein have called on the Administration to “secure” Syria’s chemical weapons stocks, something that necessarily would involve some type of military operation in Syria. The reasons for these calls are pretty obvious: a state’s use of chemical weapons against its own people (indeed, against anyone) presents an extremely troubling scenario. Plus, as Matt has noted, Assad’s use of chemical weapons may or may not implicate the Administration’s “red line.” Yet most of these articles don’t wrestle with a critical legal question: What would the U.S. government’s legal rationale be for using force in Syria in these circumstances? Julian Ku and Deborah Pearlstein at Opinio Juris noted this problem earlier today here and here, respectively. I want to add a few things to their useful reactions. I posted several months ago on possible U.S. legal justifications for using force in Syria in the face of a looming chemical weapons use or transfer. At that point, I contemplated two different scenarios: one in which Syria’s chemical weapons found their way into the hands of a group such as Hezbollah, and one in which the United States believed that Syria was preparing to use chemical weapons against its own citizens. I noted that the legal justifications for using force in the latter circumstance would be controversial under international law. My earlier post considered four possible justifications for employing force to halt an imminent use of chemical weapons by Syria: (1) an “anticipatory collective self-defense” theory; (2) an "anticipatory humanitarian intervention” theory; (3) an intervention based on the consent of the rebels, if and when the U.S. were to recognize the rebels as the lawful government of Syria; and (4) a Kosovo-like argument that force was legitimate, without an effort to argue that force was lawful. How do those arguments play out now that Syria apparently has used chemical weapons? (1) The self-defense argument remains a hard one to make, for the United States as well as for Syria’s neighbors. As I stated in the earlier post:
The USG might believe that a Syrian use of chemical weapons is likely to affect neighboring (and friendly) states such as Turkey and Jordan. Depending on where Assad used the weapons and what the atmospheric conditions were, it might be the case that the chemical weapons could drift across national boundaries – and be deemed an armed attack on that neighboring state. This might set up a theory along the lines of “anticipatory collective self-defense,” particularly where the relevant neighboring states already have asked the United States to intervene on their behalf. This is, as far as I’m aware, an untested theory.
I have seen no reports that the chemical weapons use that happened took place near Syria’s borders. One could imagine, of course, that neighboring states now will factor the Syrian regime’s willingness to use chemical weapons into their analyses about whether future Syrian military activity near its borders poses an imminent threat of armed attack (if, say, chemical weapons might drift outward from the Syrian border), such that the other state(s) could act in anticipatory self-defense. But that fact pattern doesn't seem particularly likely. (2) “Anticipatory humanitarian intervention” might now become simply “humanitarian intervention,” though as Deborah and Julian note, it’s not clear the extent to which the use of chemical weapons, as horrible as it is, materially affects the overall analysis of the humanitarian crisis in Syria. That said, states contemplating HI here surely would cite strong evidence of actual chemical weapons use as a key factor in defense of their intervention. In doing so, they would be drawing on the strong international revulsion toward chemical weapons. (3) Julian’s post suggests that the U.S. government has recognized the opposition in Syria, and so could rely on the opposition’s consent as a basis on which to use force. But the CNN article to which he cites reflects only political recognition of the Syrian opposition coalition by the United States; I don’t think it reflects legal recognition of the opposition. (An unnamed U.S. spokesperson quoted in the article says, “I think you're going to see a political recognition, not a legal recognition.”) Until the U.S. government recognizes the opposition in a formal, legal sense, I don’t think the consent argument is available to the United States. (4) As for a use of force that relies on the power of legitimacy rather than the power of law, I noted earlier:
NATO’s use of force in Kosovo was famous for its “factors” approach. Without trying to legally justify the air campaign, various NATO countries (including the United States) took pains to illustrate the campaign’s legitimacy by citing a long list of Milosevic’s bad acts. At the same time, the long list of factors (violations of previous Security Council Resolutions, failure to cooperate with the ICTY, hundreds of thousands of displaced persons, etc.) allowed NATO states to ensure they were setting a narrow precedent. The idea is that there are some truly critical, well-justified uses of force that states must take, notwithstanding the language of the Charter, but they are few and far between. The USG may believe (and probably rightly so) that it would receive little criticism if it used force to stop an imminent use of chemical weapons by a dictator against his citizens, notwithstanding international legal rules.
The legitimacy of any such intervention presumably would increase as proof of an actual use of chemical weapons grows. I hope to say more in a subsequent post about another option on the table, one that falls short of actual military action in Syria: arming the rebels. That also has implications under Article 2(4) of the Charter, something that has gone unremarked in the press and on the Hill.

Ashley Deeks is the Class of 1948 Professor of Scholarly Research in Law at the University of Virginia Law School and a Faculty Senior Fellow at the Miller Center. She serves on the State Department’s Advisory Committee on International Law. In 2021-22 she worked as the Deputy Legal Advisor at the National Security Council. She graduated from the University of Chicago Law School and clerked on the Third Circuit.

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