When their actions are criminal then they should be criminalized.
Where do you stand on kulaks? Gold bugs? Wreckers and capitalist-roaders? Other Enemies of the State?
And unilateral secession as practiced by the confederates was not Constitutional.
You'll have to prove that by quoting the document; we told you that.
As I have many times. Article IV, Section III gives Congress the power to create states and approve any change in their status, by implication this includes leaving altogether.