Adam Serwer explains what's at stake:
This point is key, and I think it's been lost in the noise -- the ACLU/CCR lawsuit doesn't seek to prevent al-Awlaki's killing as a last resort in the event that he poses an imminent danger to Americans, merely ensure that he only be killed under those circumstances. It is also trying to force the government to disclose the criteria under which American citizens are added to its reported "kill list." The government, responding to this claim, argues that the ACLU/CCR lawsuit relies on speculation that those criteria aren't actually being followed.