Under which type of government would state and provincia governments have the most sovereignty

A confederation, such as the Confederate States of America, or even the European Union, gives regional governments such as states and provinces the most power.

Confederal

Explanation:

The confederation is similar to the federation, but differs in the fact that the state and provincial governments are sovereign and their formation is made by alliances whereas in the federation this takes place by constitution. In confederation the existing ties are more lenient, whereas in the federation they are more rigid.

In the confederation there is a union of independent states and provinces which, while retaining their own government, submit to a central power, in which almost all decisions are taken in the light of the approval of the other confederate states.