“Legally, can a state secede from the union?”
There is no provision for it in law. But once you’ve gotten down to secession on the list, legality is pretty much out the window anyways.
It is completely consistent with the first, and most supreme law ever passed by the newly created United States.
The Declaration of Independence.
So I guess that means the the USA wasn’t legally allowed to secede from the British Empire, then? Because that’s exactly what we did as a nation through The Declaration of Independence.