The three part test that must be met, according to Attorney General Eric Holder, before the extra-judicial killing of an American citizen is legal are:
1. Must present an imminent threat of attack against the United States.
Would be interesting to know how the AG defines imminent.
2. Capture cannot be feasible.
This point is particularly interesting given the OBL raid and news reports like this one from CBS News:
Harrier jets flying from an amphibious carrier off the coast were ready to take a shot if the CIA drone missed. There was even an option for sending in Marine Ospreys with Special Operations Forces to collect any intelligence left after the strike, but that was never used. It was all part of a secret buildup which has occurred in and around Yemen as that country emerged as home to one of al Qaeda's most active branches.3. Must be consistent with the laws of war.
Many groups are calling for the legal memo to be released by the administration, so that the public can get a better understanding of the legal reasoning that shows such a killing is consistent with the laws of war. At this point, the government is fighting the release of that legal reasoning in court.