Just read the constitution of the CSA. Here’s a link:
http://www.usconstitution.net/csa.html
Then search for “negro” and “slave”. You get bits such as:
1. The citizens of each State shall be entitled to all the privileges and immunities of citizens in the several States; and shall have the right of transit and sojourn in any State of this Confederacy, with their slaves and other property; and the right of property in said slaves shall not be thereby impaired.
3. No slave or other person held to service or labor in any State or Territory of the Confederate States, under the laws thereof, escaping or lawfully carried into another, shall, in consequence of any law or regulation therein, be discharged from such service or labor; but shall be delivered up on claim of the party to whom such slave belongs; or to whom such service or labor may be due.
QED.
It had been a question begging for an answer since the 1700s.
Most Northern states had made their decisions regarding the disposition of slavery by the mid-1800s under the authority of their own state legislators that led to their own laws.
The South had not adopted their thinking, and that is manifest in the Confederate Constitution. Decades of legislative failure on a national level were finally resolved in a manner to erect a stable system that reduced political sabotage so often seen in the prior sixty years. As Stephens said in 1861, the issue was put to rest. When necessary, the law could be changed by legislation rather than anarchy.
At that time, it was against the logic and wisdom of the period to consider a federal intervention that involved sufficient belligerent force to coerce the peoples of sovereign states to submit to the will of others. It must be remembered that government at that time was very limited and not designed to be involved in the lives of the citizenry other than the few stipulations of the US Constitution. Crusading federal armies riding about to install the laws of one section of states forcibly on other states was a vision beyond the imagination of all but a few that saw the possibility of just that.
Those visionary few have mistakenly become known as "fire eaters". They correctly foresaw that political leaders could and would push aside the Constitution that had been explicitly designed to guarantee the rights of the people as a whole, not of a section.