The underlying illegality of all the Southern acts of secession are not the issue, I was responding to your question in your reply 131. "You are assuming that a plebiscite is required, before a State may secede. Upon what do you base that assumption?", was what you asked. And the answer was, Virginia herself. Virginia set down what she believed was needed to secede in her declaration, and that included the belief that a popular referendum was needed before seceding. Then, of course, Virginia went and promptly violated it. But respect for the rule of law was not a confederate trait.
"Illegality?" Wrong - that is precisely the issue. Otherwise, you are straining at gnats, and swallowing camels, when it comes to constitutional law...