First, he was not a foreign military. He was a US citizen and non-state actor. That is the crux of the US legal opinion on the matter, the US says it can use force against its own citizens anywhere in the world and international law does not apply because if it is a citizen, non-state actor, then it is a domestic issue no matter where the individual is located. So legally, the US makes the distinction between a US citizen joining a foreign military (state actor) and a foreign terrorist organization (non-state actor).
However, to your point if it was a foreign military while due process may not apply laws of war apply, for example, it would not be murder to kill a foreign military actor on the battlefield but it is murder if you killed a captured enemy (POW). This is applicable even in this case, because after the first botched drone strike, his father sued the US and was trying to negotiate the surrender of his son, but the US couldn't even entertain a surrender because then the US would have had to acknowledge the existence of the kill list and the fact this guy was on it. In any other context, under the law, an enemy combatant would be permitted to surrender and at least avail themselves to certain rights, like the right not to be killed while a prisoner of war. I am not suggesting or stating emphatically he would have surrendered, but I don't doubt the Father's sincerity in his desire and intent to negotiate the surrender of his son.
>"I will do my best to convince my son to do this (surrender), to come back but they are not giving me time, they want to kill my son. How can the American government kill one of their own citizens? This is a legal issue that needs to be answered," he said. "If they give me time I can have some contact with my son but the problem is they are not giving me time," he said.
I am sure the lawsuit would detail all attempts he made with the US to begin negotiations.
[1] https://www.google.com/webhp?sourceid=chrome-instant&ion=1&e... [2]http://www.cnn.com/2010/WORLD/meast/01/10/yemen.al.awlaki.fa...
The "father" and "son" I'm referencing are Anwar and Abdulrahman al-Awlaki. Abdulrahman was Anwar's juvenile son, killed in a drone strike against senior AQAP militants some time after Anwar was killed. Nasser is his grandfather.
There is no evidence in here that Anwar al-Awlaki was attempting to extricate his juvenile son from the war zone he had taken him into.
al-Awlaki wasn't a criminal and he wasn't given the death penalty. He put himself in a position of being a foreign military threat and was dealt with as a military threat. No country extends due process or the presumption of innocence to foreign military actions, and it's a tremendous conceit to suggest that the whole world's activities should be encompassed under U.S. criminal law.