I'm not a lawyer and I don't even play one after staying at a Holiday Inn Express or when posting on RedState so what follows doesn't pretend to be a legal analysis but more of a historical perspective on what Mr. al-Awlaki's untimely end may signify.
I'll preface this by saying that I think the killing of al-Awlaki to be right and proper. I'm not Ron Paul, Kevin Williamson, or Glenn Greenwald. That does not mean that I'm without a bit of queasiness.
To the best of my knowledge the killing of Anwar al-Awlaki is the first time in our history that a US citizen, serving under arms against his country, has been specifically placed on a "hit list" and then hunted down and killed.
WASHINGTON — The Obama administration has taken the extraordinary step of authorizing the targeted killing of an American citizen, the radical Muslim cleric Anwar al-Awlaki, who is believed to have shifted from encouraging attacks on the United States to directly participating in them, intelligence and counterterrorism officials said Tuesday.
It isn't as though this is business as usual, the compilation of such a list represents a first:
It is extremely rare, if not unprecedented, for an American to be approved for targeted killing, officials said. A former senior legal official in the administration of George W. Bush said he did not know of any American who was approved for targeted killing under the former president.
There are several possible models for this action but as we will soon see they all fall short.
Throughout history there have been certain classes of criminals subject to extrajudicial killing. Pirates, for instance, were condemned as hostis humani generis, or enemies of mankind, and subject to summary execution wherever they were taken. The fact that this was authorized does not mean that it has happened since the dawn of the 18th century. When Robert Maynard defeated Edward Teach at Ocracoke Inlet he brought the captured pirates back to Williamsburg, VA for trial and execution. I have yet to find an example of a US warship taking pirates and hanging them on the spot.
Finding men of your own country in the army of your opponents is hardly a new experience. Throughout history when such men have been encountered they were given short shrift (there are obvious exceptions to this global statement, "na Geana Fiadhaie", the Wild Geese, frequently found themselves on opposite sides and were rarely treated as anything but honorable combatants). During the Mexican War, a number of American soldiers deserted to the Mexican side and formed the St. Patrick's Battalion, or San Patricios. When they inevitably fell into American hands a goodly number of them were hanged. Even so, this was done after court martial and the leader of the San Patricios avoided the death penalty because he had deserted before the declaration of war.
So while bearing arms against your native country usually resulted in death if captured, it is distinguished from al-Awlaki in that there was no list involved, the people are captured, and there is at least a patina of judicial process.
After the Civil War there was assorted score settling against some Confederate guerrillas, e.g. Marcellus Clark and Champ Ferguson to name two, but they were tried by court martial no matter how flawed the process, for instance, Clark's verdict was signed before his court martial started.
Perhaps cattle rustlers and horse thieves were legally hanged out of hand in the Old West. I don't know and I can't find evidence that the law allowed this rather than the law merely looking the other way. In either case, it would not rise to the level of the killing of al-Awlaki as there was a judicial imprimatur on the action.
When Prohibition ushered in an age of organized crime, law enforcement changed its rules of engagement. The killings of Bonnie Parker and Clyde Barrow from ambush and the gunning down of John Dillinger on a Chicago sidewalk would not pass muster today. However, these killings involved indictments and arrest warrants.
During World War II we had the celebrated case of the German saboteurs who participated in Operation Pastorius. Two of these saboteurs were American citizens. When they were captured they were tried by military commission and died in the electric chair in the old District of Columbia jail.
Again, capture, trial, execution.
One has to assume that some of Otto Skorzeny's commandos who participated in Operation Greif were American citizens, some had lived in the United States for a long period of time. When they were shot, it was after a court martial.
There might possibly be analogs in the classified history of the Cold War, that era of James Bond and his "license to kill" but they remain lost to us. What we can surmise is that the killing of defectors and traitors was much more common in novels than in real life. Guys like Philip Agee and Edward Howard weren't targeted as far as we can tell.
Wikipedia tries to make a big deal out of "targeted killings" but a review of the names find that they are uniformly enemy combatants who were killed. What they do have in common is that they have all happened after 9/11. There is another American on the list, the hapless Kamal Derwish, who seems to have serendipitously been in the wrong place at the wrong time rather than specifically targeted.
There are times in history when law and custom are outstripped by social change and technology. I think we are at such a juncture in warfare. We are now, for the first time, actually able to locate particularly noxious individuals via various intelligence methods and kill them via Predator.
What leaves me queasy is the idea of a list.
If you are gunning for a bad guy his nationality should be immaterial. Americans do not have a get-out-of-jail-free card on the battlefield. The fact that he is on the wrong side in an armed conflict makes him a legitimate target. You don't need a list. It makes no difference whether you are hitting him with a Hellfire missile or a Delta Force trooper drags him out of a car in Albania and shoots him by the roadside.