I would agree with your reading and at the same time I also think it is morally sound to go to war with the South to free up the slaves from the South.

The south was allowed to assemble, talk and vote on it, but the north didn't recognize the secession as legitimate. Those are separate issues.

Catalonia has been allowed to discuss. It’s just the referendum, as I understand it, that is being banned. I’m trying to think what would happen if California passed an independence referendum whose results were then nullified by the Supreme Court.

So they can talk about independence but not vote on it?

Independence would be a modification of the Spanish Constitution, which can be voted on.

Not that guy here but yes as someone who is pro self determination I think the Kurds should be allowed to leave Iraq and the South should have been allowed to secede.