The statists love to bring up Texas v White.
Good analysis here:
Basically it says that the decision doesn’t cite any constitutional basis and couldn’t because there’s nothing in the US constitution addressing leaving the union, which per the US 10th amendment means that power is left to the states.
Further. they say that “It is also noteworthy that two years after that decision, President Grant signed an act entitling Texas to U.S. Congressional representation, readmitting Texas to the Union.” Why readmit Texas if the Supreme Court said they never left?