Republican (constitutionalist) former President Jefferson writes in a letter to William H. Crawford, Secretary of War, writes on the Article X of Amendment power of the States to secede from the Union”: “If any State in the Union will declare that it prefers separation … I have no hesitation in saying ‘let us separate.'”
[added 12/4/2021]
Subsequent Events:
References:
Thomas Jefferson to William H. Crawford, 20 June 1816
en.wikipedia.org/wiki/William_H._Crawford
Was the Union Army’s Invasion of the Confederate States a Lawful Act? by James Ostrowski
www.lewrockwell.com/ostrowski/ostrowski31.html