I am afraid I cannot be of much help with [the question of whether there is a legal right, enforceable by the Supreme Court, for a state to secede], 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 agree entirely with Justice Scalia that a state cannot claim in court a legally enforceable right to secede. Following the Civil War, the Court held that states lack such a right to secede. But I suspect that even before the Civil War, the Court wouldn’t have held in favor of a right to secession, whether on the merits or under the “political question” doctrine. Just a it wasn’t for the Court to decide whether a highly unrepresentative state government had an insufficiently “Republican Form of Government”, so I don’t think that it would be for the Court to decide whether the United States should let a state (in the question to which Justice Scalia was responding, Maine) leave the union.
And I doubt that Justice Scalia is saying anything beyond what a court could do. That, after all, is the question he was facing (asked by a screenwriter): “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.... If you could spare a few moments on a serious subject that is treated in a comedic way, I would greatly appreciate your thoughts.” Whether a state can successfully claim a right to secede, before the nation at large (presumably in persuading the nation not to use military force to keep the state from seceding) is a separate matter.
On that, I stick by my earlier views, and I don’t think that Justice Scalia’s comment is to the contrary (though I’d stick by my earlier views even if he did intend his comment to cover a political claim of right, at least absent further argument explaining why my views are mistaken):
Whether there is a moral right to secede, which the nation as a whole should respect, must be a judgment based on how we see the world today, not based on what happened 144 years ago. A matter is “settled” by political decision only so long as the political decision commands the adherence of the polity. If in 2065 Alaska, California, Hawaii, or Texas (just to consider some examples) assert a right to secede, the argument that “in 1865, the victorious Union government concluded that no state has a right to secede in opposition to the wishes of the Union, so therefore you lack such a right” will have precisely the weight that the Americans of 2065 will choose to give it — which should be very little.
And beyond that, even if there is some precedent of some sort properly set by the Civil War (and I continue to disagree that there is), any such precedent can’t tell us much about consensual secession. The talk I occasionally hear of secession (again, talk that I think is not really serious) is not about departure in the face of military opposition — it’s about creating a political sentiment in some place in favor of seceding, and a political sentiment in the rest of the country in favor of allowing the secession. The results of a bloody civil war tell us nothing about the propriety of a Velvet Divorce.
Appomattox might well have a continuing effect (as does Philadephia) on the psyche of today’s Americans, and of future Americans. Its immediate effect also deeply influenced the economic structure of the nation, and the political structure of the nation’s political institutions; I suspect this also makes future secession less likely.
But that’s not a “settlement” of the secession question for the centuries. And there can be and should be no such settlement. “The past is a foreign country: they do things differently there.” So the present is different from the past, and the future from the present. Poetic allusions to a peace treaty resolving one particular conflict can’t tell us what is right to do in our country today.