For what it's worth, I've noticed that most of the attorneys saying this are liberal attorneys. If you read the entire article and section of the Constitution (III/3), you'll see that (1) war need not be declared for it to be applied, and (2) merely giving "aid and comfort" to the enemy is enough grounds. Last night I caught a few minutes of Nightline, and noticed that even the creepy attorney Kuby (don't recall his first name), although mentioning possible defenses, thought Walker might be in deep trouble.
Folks, until we hear something directly from the admin on this issue, let's not assume that these "opinions" being expressed via NBC and Reuters came from anyone who has a say about what's going to happen. Let's wait for a direct statement. Perhaps in one of today's press conferences, a reporter will ask the question, and someone will give an answer. Then we can either relax, or get our dander up, whichever applies.
I'll bet his lawyers (which he's been denied aid and comfort from so far) would argue that it wasn't his intention to be a traitor and fight against the USA, even though he has said publicly that the Taliban is right.
What else could be next?