[Non-Sequitur]

I never understood the idea that somehow a war decides a constitutional question.

It didn't. Texas v White did in 1869. But even that case left open the option of secession with the consent of the other states so I don't know where Justice Scalia got his 'no secession at all' position.

[cowboyway]

But even that case left open the option of secession with the consent of the other states

You left out part (as usual):

"except through revolution or through consent of the States"