But it was the remedy that the South chose in 1861. They left with out discussion, walked away from debt obligations, and took everthing they could get their hands on. If their solution was unconstitutional then how could Lincoln be accused of violating the 10th Amendment by opposing it?
The Southern states had a lengthy list of grievances, not the least of which were numerous violations of article IV section 2 of the Constitution.
The only relevant question is did those violations render secession legal?
Texas v. White says no. But that opinion seems to be founded in the notion that the territories/states/peoples were bound at the hip in perpetuity simply because there is some commonality in purpose. Yet it also says.."There was no place for reconsideration or revocation, except through revolution or through consent of the States.
So assuming it's 'illegal' to secede, what, if any remedy can the General Government have legally sought?
According to Kentucky v. Dennison, none.
"...there was "no power delegated to the General Government...to use coercive means to compel" a state governor to act.