A constitution is a foundation which can only be changed by the means proscribed within it. It is not an ordinary law. An amendment allowing withdrawal would be the constitutional means to change the Union. The purpose of the document was to make the UNION stronger, more perfect.
Even the foundation it superceded declared the Union to be “perpetual” hence a “more perfect” Union is no less. All the significant Founders: Washington, Hamilton, Madison etc. declared withdrawal impossible. Not even Jefferson suggested the contrary.
Certainly the means of testing the theory, an insane attack on clearly federal possessions obscured the legal issues and made it much easier to rally behind Lincoln as even some Democrats did.
You want to research this fantasy of yours?
Noted Anti-Federalists
* Patrick Henry * Samuel Adams * George Mason * Richard Henry Lee * Robert Yates (politician) * James Winthrop * James Monroe * Mercy Otis Warren * George Clinton