What I like to call "Having your cake and seceding from it, too."
That is rather like the lost causers who claim that the insurrection was not bound by the Constitution because they pretended to secede from it, but Lincoln was forbidden to put down the insurrection because those who made war to support the insurrection should have been protected by the rights under the US constitution.
In like manner, the slave power complained when the free states set conditions (such as common rules of evidence) for their cooperation in enforcing the Fugitive Slave provision of the US constitution. Then, when such provisions were struck down, so that only federal authorities could enforce the Fugitive Slave Acts, the slave power complained because the free states were not sufficiently cooperating with the slave power.
They really didn’t like that the free states were free. In that way, the slave power was opposed to states rights.