[Non-Sequitur]

The secession acts of the People of the Southern States, with the arguable exception of that of Arkansas whose legislature acted for that State rather than the People, were and still are "legal" -- in fact, they are above "legal", they are supraconstitutional, beyond the reach, and beyond the scope and review, of any government or court.

If that's your gold standard for valid secession then you should probably take issue with a number of other states. South Carolina, taken into rebellion solely by act of the state legislature without referendum. North Carolina, taken into rebellion by act of the state legislature despite a popular referendum against secession. Virginia, admitted to the confederacy and taking arms against the federal government before the popular referendum was held. And so on and so forth.

...in fact, they are above "legal", they are supraconstitutional, beyond the reach, and beyond the scope and review, of any government or court.

But here on planet Earth we generally refer to those as 'rebellion'.

[lentulusgracchus]

But here on planet Earth we generally refer to those as 'rebellion'.

There was no rebellion, just as there was no rebellion whenever King Edward VII changed his trousers.