As an aside I feel Miranda rights have been taken too far, but I'm not aware of any exemption from them for unconvicted traitors. Once convicted I'd give traitors everything allowed when the 8th was ratified.
I don’t know that he has met any of the elements of treason, but perhaps the investigation will reveal something. The spy case that I was involved with was certainly treason, but that charge was never brought, only espionage. In fact, that dirtbag was tried in a German court, not a U.S. court.
A U.S. citizen can become an enemy combatant, but he would need to join a military or insurgent group that is an enemy of the U.S. Probably doesn’t apply here.
This guy will soon have one of the Left’s best lawyers who will go after any misstep by LE.