What is true of any Individual is therefore, necessarily, logically true of any Group of Individuals (and therefore of any of the several States).
I wish the rebs had followed that principle when the 1861 Greeneville convention of East Tennessee expressed the desire for the region to secede from the rest of the state and remain in the Union.
Of course when Confederate lip service to noble ideals conflicted with power lust, principles lost. The CSA was nothing but a power grab for slavery which was only sometimes obscured with appeal to the higher American principles.
As far as the Greeneville convention, you're certainly correct.
The Southern States enjoyed a Natural Right to Secede from the US Federal Government, and Greene County enjoyed a Natural Right to Secede from Tennessee and seek re-admission to the USA.
Obviously, it was morally wrong for Tennessee to deny Greene County's Natural Right of Secession, just as it was morally wrong for the US Federal Government to deny the Southern States' Natural Right of Secession.
Glad we're in complete agreement.