I'll concede that it certainly has been interpreted by the Supreme Court (as is their duty) to be the case that secession is unconstitutional and a right not granted to any state. The principle of stare decisis would suggest that's the way it is and will be, but like you said, who knows what the future will hold.

But whether or not the court was correct in interpreting things that way was not my original argument. It was that to say someone is wrong for claiming secession is treason and calling them a "revisionist" is ignoring the reality of the situation and is ignorant of history.

Good point. I don't know the answer, and I debate both sides of this one.

Of course "Revisionist" is an epithet usually thrown by someone whose opinion differs from his target, and rarely reflects any actual knowledge of history.