A secondary question regarding incitement is whether Anwar al-Awlaki's speeches celebrating and encouraging the killing of Americans meets the standard of "imminent lawless action” set by the Supreme Court case Brandenburg v. Ohio. The case involved a white supremacist leader who was calling for "revengeance" against blacks and Jews. The Supreme Court decided that there had to be a danger of "imminent lawless action" to cross the line from protected speech into incitement -- like, say, if someone said you deserved to be shot and their buddy next to them was pointing a gun at you.
As far as Anwar al-Awlaki's speeches go, the administration might argue that they represent an imminent threat because they might inspire someone like Fort Hood shooter Nidal Malik Hasan to action, but that seems like a stretch. Brookings Scholar Ben Wittes says that "It does beg to some degree the proximity or imminence question, are you someone, if they don’t take you out right now, we’re going to suffer right now, or would it just be more convenient to so.” Sounds like we're getting into Bush-like questions of preemption here, and I'd just like to point out those haven't worked out so well.
As abhorrent a human being as Awlaki might be, I think this version of the self-defense argument for assassinating Awlaki is a real stretch.
UPDATE: I misunderstood Mr. Wittes. He clarifies in an e-mail that while there is a question of imminence involved in whether killing him would be an act of self-defense under international law, the Brandenberg standard doesn't apply here:
Just to be clear: The standard the Supreme Court articulated in Brandenburg v. Ohio has nothing to do with the question of whether it is lawful to target Al Awlaki or not. It merely has to do with the question of whether the latter's speech is constitutionally protected. The question of whether it is lawful to target him is a different question under the law. According to the administration (and I agree), it is lawful to target him if either he is part of enemy forces under the AUMF or if he poses a threat such that targeting him would be an act of self-defense under international law.
The word "imminence," to be sure, has application in both questions. In Brandenburg, as you note, the standard for incitement is "imminent lawless action"; and in the self-defense inquiry, there is also an imminence or proximity requirement to the threat before one could call an attack anticipatory self-defense, ie, it is not enough that there be some threat at some time. There has to be some kind of unfolding chain of events that, without interruption, will lead to the harm against which one is defending oneself.
-- A. Serwer
