Mike,
Many may not know, that our US Contitution prior to 1861, had mentioned in one of the admendments that was later removed, about the rights of states. Also the Bill of Rights mention rights of states, but the Federalist papers mention - that it was the right of any state in the union to remove itself (from the union), if they felt that the central government was getting over powering or not meeting the needs of any such state; which leads to another discussion of States Rights. We as a nation abid by all these rules and regulations, set by our forefathers.
They were not perfect, nor did they think they were, but they did leave areas oper to revise at a later date.
Secession was no different. It took until 1866 to revise the Constitution (& laws) of our land, to make sure that secession would not be possible in our nations future.
South Carolina had problems (of sort) playing well with others (the US Govt), since the start of the American Revolution, for many reasons beyond my knowledge or time...Since then I do know they (SC), had tried to seceed 1830's and in the 1850's.
Since the talk of session through the years, I am supprised that it took them that long to remove themselves from the union.
Being involved with the SCV, and having a Mother-in-law living in Columbia, SC - I keep up with news from around the state of SC. Last I heard, SC wants to again leave the union...For again what-ever reasons beyond my understanding.
Only difference is that TODAY there is no ordinance in the US Constitution to allow that to happen as prior to 1866....
I have to look up some info to confirm your original question, in a wonderful book on Polotics before and during the WBTS, called...
Blood Stains..... It is a two book Vol set, regarding the polics, issues, views and the players of the period.
I hope to have some answers for you shortly
Steve