In fact, it's not legal to try American civilians in Military Tribunals, per long standing Supreme Court rulings going back to the Civil War, when Abraham Lincoln tried it.
And, way back then the SC held it was impermissible (with a Civil War going on) it's completely implausible that it's going to happen now, when the entire Federal Court system is up and running normally.
One reason I've always felt the 80,000 sealed warrants, military tribunals, GITMO detention theory was a fantasy. Still seems that way.