It was about states rights, but possibly not as you may think.
The Federal Fugitive Slave Act required northern states to assist in the capture and return of escaped slaves to their self-styled "owners".
Many northerners were outraged by this filthy law and acting as private citizens, or through their local and state governments, subverted it.
What the south wanted was for northern states to surrender their states' rights and knuckle under to this federal law. When it became clear that this was not going to happen, secession ensued.
Ill bet you didn’t know this. Whe Lincoln signed the emancipation proclamation. He did not free the Northern Slaves. You can’t make that up. All about states rights.