[Non-Sequitur]

...and under these limitations, have the people of each state in the Union a right to secede from the confederated Union itself.

Not unilaterally, no.

[central_va]

Not unilaterally, no.

The only state to unilaterally secede(so far) was S.C. When Mississippi joined S.C. the 'unilateral' part went out the window.

[Idabilly]

Not unilaterally, no.

Well, I disagree.

Proper methods of Secession would include horizontally, trilaterally, unilaterally, cross circumferentially, and in single file.

Hope this helps :)