States were added by acts of Congress. It logically follows the same can be done in reverse. But it needs to be on agreed upon and mostly amicable terms, or th

States were added by acts of Congress. It logically follows the same can be done in reverse. But it needs to be on agreed upon and mostly amicable terms, or the state(s) desiring to leave will be unable to get the necessary votes. The southern states trying to take their slavery and go home knew this for decades before, so they didn't even bother.