Slavery nor any reason was mentioned in the CSA Constitution. You are confusing the ordinances of secession with our CSA Constitution.
Slavery was mentioned in the CSA Constitution.
Numerous times.
That's specifically was the primary purpose they founded their "nation" on - Slavery was their Cornerstone.
One remarkable thing the CSA did was also not allow slavery ever to be abolished. Ever. Our Founders allowed a mechanism for slavery to be abolished.
Not so the the CSA.
When the framers of the Confederate Constitution wrote it, they went out of their way to make sure they would ever be deprived of their human black property.
They founded their nation on being a
perpetual slave "nation." -- and any new state joining the CSA in the future was
required to be a slave state..
How's this humdinger: Article I Section 9 of the Confederate Constitution : “No bill of attainder, ex post facto law, or law denying or impairing the right of property in negro slaves shall be passed.”
This one? Article IV Section 3: “The Confederate States may acquire new territory; and… In all such territory the institution of negro slavery, as it now exists in the Confederate States, shall be recognized and protected be Congress and by the Territorial government; and the inhabitants of the several Confederate States and Territories shall have the right to take to such Territory any slaves lawfully held by them in any of the States or Territories of the Confederate States.”
Expanding, preserving, protecting and defending ownership of human beings was what they were about.
And they were ready to fight to the bloody death their right specifically to own humans and profit richly from their population of nearly half slaves. (nearly 4 million out of a total population of 9 million.)