How about Penhallow v. Doane?
Majority of that Court held ( secession was legal )
Well, no. Not really. First off, Penhallow concerned events before the Constitution was ratified. Before, even, the Articles of Confederation. It concerned events which took place under the Continental Congress. If New Hampshire had wanted to withdraw from that, they certainly could have. But having not withdrawn, they were subject to the courts’ authority.