Secession is a sovereign act of the People, and secession conventions are just like conventions to ratify or amend the Constitution. There is nothing "treasonous", either now or in 1861, about secession.
Chief Justice Chase, in his 1869 opinion in Texas vs. White (from which, btw, he should have recused himself, having been a Lincoln cabinet member through over three years of the Civil War), said that secession ordinances were null, void, and illegal. He lied through his teeth. The dissent was better law, but he was a political hack put up there in the CJ's chair by Lincoln himself precisely to do what he did: Homer for the Lincoln Administration and its prosecution of the Civil War.
Admitting that secession was legal and that Texas had done it the right way (Arkansas may not have) would have put Lincoln's War in a whole new, and unflattering, light.
Are you a Constitutional Lawyer? Are you saying people can, both in writing and verbally, petition their state’s legislature for the Secession from the United States without fear of retribution from the Federal Authority?
ROTFLMAO!!!!
But the past is past, let's look to the future. How do you accomplish secession now? Assume for the moment that unilateral secession is legal, how do you go about it? Do you allow the legislature to appoint a committee to vote on it and decide to secede, like South Carolina did? Do you hold a state referendum to vote on the issue? If you do, then should it be a simple majority that takes the state out of the Union or a super majority? What if 50.001% vote to remain, what do those that voted to leave do now? What if a majority vote to stay, but the governor and the legislature announce secession anyway, like North Carolina did? Or what if the governor and legislature announce secession and promise a referendum later to approve it, like Virginia did? Are either of those valid?
The cases were trumped up - White, Chiles and Hardenburg had numerous cases before the courts. IIRC, Freeper Nolu Chan proved a few years ago that the cases where shams.