You have yourself have stated that the people can call a constituional convention to disband the government.
If you are going to break up the Union, that it should have followed constitutional means.
free dixie,sw
The departing States didn't liquidate the Union. They merely withdrew themselves. They didn't need the consent of the full Union for that. They would have, if their purpose had been to abolish the Union entirely, but it wasn't. Each State's People spoke for themselves, and left the Union.
Their secession conventions were perfectly legal (Arkansas probably excepted), and their mode of withdrawal fully protected by the Constitution itself (Ninth and Tenth Amendments) -- as if they needed that, to speak and act for themselves, which they didn't, but nevertheless their acts were fully protected.