Should states be allowed to have slavery if they wish?

Don't be silly 

He's not (or, not really).

There was a recent discussion here about "states rights" and defenders of "states rights" cannot offer a principled reason why their interpretation of "states rights" would not include the ability of state and local governments to reimpose slavery and/or Jim Crow.

Hey, I looked up State's Rights for Old Schools question and it looks like that is how the whole thing took root (no pun) in the first place. 

I thought there had been a war to settle the issue