Since the ratification of the Constitution no state has 'freely joined' anything. They were allowed to join and only after obtaining the approval of a majority of the existing states as expressed through a vote in Congress. Should leaving require the same?
The fact remains those territories joined of their own ‘free’ will. And, in case you have some errant misconception I didn’t know about your trivial reply to that which you weren’t addressed is meaningless. Stalk much, vaxxer?
No, because our founding document (Declaration of Independence) says they have an expressed right to leave if they wish, and in historical context, all states that left under that document, did so without permission from the "Union".