You've got to love that Antonin Scalia answered a letter from a screenwriter asking for tips on a screenplay involving Maine seceding from the union:

I am afraid I cannot be of much help with your problem, principally because I cannot imagine that such a question could ever reach the Supreme Court. To begin with, the answer is clear. If there was any constitutional issue resolved by the Civil War, it is that there is no right to secede. (Hence, in the Pledge of Allegiance, "one Nation, indivisible.") Secondly, I find it difficult to envision who the parties to this lawsuit might be. Is the State suing the United States for a declaratory judgment? But the United States cannot be sued without its consent, and it has not consented to this sort of suit.

I am sure that poetic license can overcome all that — but you do not need legal advice for that. Good luck with your screenplay.