LOL! So if someone does something legal, and someone else does something illegal to stop them, does that make the illegal act legal?
However true, therefore, it may be, that the judicial department is, in all questions submitted to it by the forms of the Constitution, to decide in the last resort, this resort must necessarily be deemed the last in relation to the authorities of the other departments of the government; not in relation to the rights of the parties to the constitutional compact, from which the judicial, as well as the other departments, hold their delegated trusts. On any other hypothesis, the delegation of judicial power would annul the authority delegating it; and the concurrence of this department with the others in usurped powers, might subvert forever, and beyond the possible reach of any rightful remedy, the very Constitution which all were instituted to preserve.
James Madison, Report on the Virginia Resolutions
The States ARE 'the parties to the compact', BTW.
I do understand all that, but “a page of history is worth a volume of logic.” The War of Northern Aggression is a huge precedent.
Why would a nation let a state just leave if it could be sold?