Mind you, I am, as I stated in my first post, profoundly disturbed by this manifestation of new-age warfare. AC probably made the thing moot by suggesting that the evidence is strong that the fellow was not a U.S. citizen, but in fact I’m beginning to find your suggestion persuasive, if I may paraphrase: in the case of a U.S. citizen in a similar regard, a treason trial is very much in order. I don’t think the prosecution would have a great deal of trouble finding two witnesses, and I would have to wonder if the accused’s own public statements might not constitute open admission in court, but those are issues for lawyers and are essentially irrelevant in discussing this as a matter of policy. Bearing in mind I’ve just put words in your mouth, if I understand them correctly I’ll have to concede the point.
Some sort of a “trial” would certainly be appropriate, though there’s no reason for it to take the form that we in this country generally envision as a “trial” (jury, prosecutor, defense attorney, etc).
Something more akin to the tribunal held for the Operation Pastorius participants would be fully adequate to hear and consider the testimony of the requisite two (or more) witnesses to his treason.
Once convicted, he would be sentenced pursuant to existing law established by Congress, again, in keeping with Article III Section 3 of the Constitution, and, should the sentence be Death, then fire-up the drone.
Everything fully legal and Constitutional.