It seems to me we can just dictate it is ok to kill someone who is not in a war zone without any traditional war being waged by them.
We have not done any such thing, at least not in the last two years, as part of an authorized military action.
Some soldiers got kind of out of hand after rummy and the rest of the merry morons did the damage that they did to military discipline, but that was dealt with as criminal activity.
The merry morons ordered criminal activity and called it "intelligence gathering." There was nothing intelligent about the way the useless drongos conducted the war. Many of the civilian deaths during their interregnum may have been the result of the kind of intel that you get from a prisoner when he is being water boarded, which is to say,
total crap that makes the torture stop. If you think you are going to die if you don't offer them something, why not roll over on the neighbor who offered a better dowry and political connections to marry the girl you really wanted?
Civilized interogation techniques like those spelled out in the Army FMs on the subject produce far more reliable intel, and better intel leads to better targetting and better targetting leads to a drastic reduction in ther number of civilian casualties.
No, don't bother crying for Anwar al-Alwaki. He joined an enemy guerilla formation and was operating in a nation that was conducting operations against that guerilla formation. Totally legitimate target.