There is no unilateral legal "right of secession" as the secessionists of "the South" attempted in 1861. Generally, the result of the Civil War is the de facto decision on that. The 1869 Texas v. White et al decision is the last word from the Supreme Court on it, and the XIV Amendment contains some provisions that were imposed to punish those who rebelled."I’m a screenwriter in New York City, and am writing to see if you might be willing to assist me in a project that involves a unique constitutional issue.
My latest screenplay is a comedy about Maine seceding from the United States and joining Canada. There are parts of the story that deal with the legality of such an event and, of course, a big showdown in the Supreme Court is part of the story.
At the moment my story is a 12 page treatment. As an architect turned screenwriter, it is fair to say that I come up a bit short in the art of Supreme Court advocacy. If you could spare a few moments on a serious subject that is treated in a comedic way, I would greatly appreciate your thoughts. I’m sure you’ll find the story very entertaining."
The Constitution offers little that would point to a legal way out. Most likely, the Supreme Court would punt the issue over to the Congress as being rightly a "political matter" that the Court could not decide. If you want a Supreme Court decision to free Maine, you would need to postulate and prove a violation and an injury to the State of Maine so overwhelming that the only possible remedy the Court could provide would be to free Maine of the obligation she undertook to be part of the "perpetual Union".