Not neceesary. The USC is silent on the issue of secession. Nothing prohibiting it.
I think the civil war decided that though. But there is no dispute that secession is allowed if you amend the constitution to allow it. You would have a hard time getting the number of states needed to approve it now. But if the libs continue to degrade the unity of the nation I think it could happen. For example if the government can’t pay the national debt…. That might be the trigger.