It's unclear whether this legislation allows or was intended to allow the murder of Americans by drone.
Yeah, you keep using the emotionally loaded language. This is, at the moment, a legal discussion. In a legal context, "murder" is what you have after you have shown the killing was not legally justified (*legally*, not morally). I raise the point because, just as you are not supposed to murder people, we also have a big thing about folks being innocent until proven guilty.
The legislation is amazingly brief. It does not spell out some forces that are allowed, and others that are not. It says, "...the President is authorized to use all necessary and appropriate force..." - failure to give express capabilities must have been intentional, the Congress was enabling broad powers. Nor does it say that American citizens are not to be targets of this force - if they're part of, aiding, or abetting Al Qaeda or their operations, they were potential targets.
Right. A note by an attorney saying, "I think it's okay." is all that was used. He got no clarification from a court on whether it was okay or not. Instead, he went on his own.
Since Congress had already authorized broad and unspecified capabilities, that's *more* than was really required. Soldiers don't generally wait on courts for authorizations to shoot particular enemies.
We don't know if it was intended to allow the use of lethal force to murder Americans. It was used that way, but as you noted, it was supposed to be used against Al Qaeda, not U.S. citizens. Where one is both, it may not allow the use of that force.
There is *nothing* in the legislation that even vaguely suggests that US citizens are excluded. Such an interpretation is not supported by the text.
So, you may have a problem with the AUMF, in concept or execution, but given the AUMF, proving this was not legal is difficult.