Seceding should be a democratic vote. The pre Civil War American South did not allow blacks to vote, so no democratic vote to legitimize a secession decision was possible, just like how Putin does not sponsor truly democratic secession votes in Donbas or any of the other splinters he's created. This is the best way to conduct secession votes: https://medium.com/non-violence/stakeholder-control-avoiding-war-thru-flexible-democratic-boundary-shifting-bf6f9c20e578