LOL!
Having to ask permission to leave a voluntary association would negate the entire concept of sovereignty.
Having the right to withdraw from your country anytime you wish for any reason or no reason would negate the entire concept of a country or nation or patriotism.
"Sovereignty" of states or regions or localities in your sense is a recipe for civil war. The idea that some part of a country can walk out on debts and obligations whenever it wants and take away as much territory as it dares is one that inevitably leads to armed conflict.