And once a state has withdrawn from the Union, U.S. law no longer applies.
Not possible under U.S. law.
A state might withdraw under natural law, but it would have to make a better effort than the rebels did in 1860-65. Theirs was pretty lame.
Walt
As I've said, Wlat, law is not just made up as we go along. And regarding the Militia Act, it states insurrection, not withdrawal. What's your next desperate grasp at the quickly-receding straws going to entail, an appeal to the U.N. Charter?