Bull. The same confederate constitution that protected slave imports also contained a clause that stated "No bill of attainder, ex post facto law, or law denying or impairing the right of property in negro slaves shall be passed." Slavery wasn't going anywhere if the confederate founding fathers had anything to do with it.
The law in question prevented the Confederate government from interfering with the states - they could end slavery within their own state. The Confederacy did enact a law that required that Union slaves captured on Union ships to be returned to the state of origin and freed by that state's Governor.