Sucession was not Constitutional no matter what anyone says or how they CHOOSE to interpret the Constitution. Texas is the only State that has ever had the express right to sucede from the Union as put in the agreement allowing Texas to join the United States. NO OTHER of the 49 States has that right in the Constitution. Never have. The presumed right to secede is based soley on the slave owning Confederate States interpreting the Constitution as lining out a Confederacy form of government where the people answer to their state Government, and those State governments answer to each other and the Federal Governemnt as a courtesy not a requirement, with the belief that the State Senates of any given State can vote to break away from the Federal Government and the United States if they feel that the United States has "breeched" the contract of the Constitution. That assumption is NO WHERE in the 1860s incarnation of the U.S. Constitution. They considered the fast approaching Senate vote which would vote down slavery as justification for breaking away. There are other excuses but that's the bottom line. There was no legal basis in the Constituton for that act of treason executed by the Confederate States in breaking away from the United States. It was unfounded, illegal, and had no justification.
well tell that to Rawle who wrote a book on the matter a book that was used at West Point.