Justifiable homicide is not some terrifying new idea. Government agents are allowed to kill terrorists, whatever nationality they are. This just seems to recognise in law the fact that al-Awlaki is a member of Al Qaeda and is subject to the consequences of that status.
You obviously have no idea how government agencies work. Every bullet fired from a government agent's gun means a pile of paperwork. And if someone is killed by that bullet it means inquiries, because for something to be a justifiable homicide, it has to be proven
to be justified. Most government agents never discharge their firearms in their entire career. Despite what TV has told you there is no "licence to kill" which gives any agent the right to shoot terrorists willy-nilly. They have no more right to kill than the average citizen does, which is to say in defence from a clear danger. This is why the CIA has
a list in the first place. This list does not include 'every member of Al Qaeda', but rather select individuals that are believed to be, by their very continued existence, unacceptable threats to the safety of the nation. It is not a good precedent to set that American citizens can be placed on this list without trial. It in fact violates the constitution in multiple ways and ignores established procedures for dealing with this.
Hasn't been tried for 9/11, which you must admit sort of sparked all this interest in him off.
Either you are very young or 9/11 eclipsed lots of other stuff for you (not surprising, many Americans only believe things are wrong if they happen in America). Bin Laden was active for years, maybe even decades, before 9/11. But that is beside the point. Osama bin Laden was not a naturally born US citizen.
The point is that members of Al Qaeda do not need to be tried in court before our soldiers and agents are allowed to kill them. Presuming that nobody here has a problem with that, the only controversy here would seem to be if this guy's membership in Al Qaeda were in doubt, which doesn't seem to be the case, so I don't see the problem.
Again, not even the military gets to kill people just because they are part of Al Qaeda. They must be a clear, armed danger. Rules of engagement are very specific on this and soldiers that violate them are tried and disciplined within the military court system. It is very rare to set up a kill list and the names on that list should be there with no other alternative, and your rights as an American citizen should prevent you from being put on such a list at all. It is a clear violation of constitutional rights. They could have tried him for treason (there are methods for trying people in absentia
in unavoidable circumstances). They could have stripped him of citizenship. They didn't.
To appeal to the pragmatist consider the precedent this sets. Even if you can approve of this realize that the next time it is applied it might not be a situation you agree with. This is a big blunt instrument being given to the executive branch with no oversight by the legislative or judicial. That is a recipe for disaster.
If you will indulge my hyperbole for a moment, this is Pandora's box, and it is baffling to think that you are so short-sighted as to be cheering its opening.