Then the obvious question is what does one have to do with the other?
You conveniently forget the above court case, don't you?
What, Scott v Sandford? No, I didn't forget it. I actually read it. Congress could not ban the movement of slaves into the territory but nowhere does Taney imply that states could not ban or restrict it.
Not in the least. The Corwin Amendment barred Congress from creating any amendment to alter the patterns of slave ownership. The Confederate Constitution made no such limitations.
On the contrary, the confederate constitution did not allow the confederate congress to pass any legislation impairing the ownership of slaves. The confederate constitution also required the congress, on the demand of any three states, to summon a convention of all states to consider constitutional amendments. So you are presented with a contradiction. In order to amend the constitution to prevent slavery, the confederate congress would have to call a convention of the states. But that same constitution forbids the congress from taking any actions that impair the right of property in slaves. What takes preference? A nice question for a confederate supreme court, had there been such a body that is.