Contract indentures the parties, waives FSIA: to retain 'sovereign immunity' is to have a separate entity to act as intermediary, like Read about a real life recent instance of a Sovereign Nation waving sovereignty because they didn't use a wholly separate entity intermediary: https://guardian.ng/features/law/legality-of-waiver-of-sovereign-immunity-clauses-in-international-contracts/
Or to the People: Popular Sovereignty and the Power to Choose a Government http://cardozolawreview.com/popular-sovereignty-tenth-amendment-reese/
There is a set of powers relating to the federal government, but not delegated to it, that states cannot have reserved because they lack prior ownership. Those powers must belong to the people. In addition to the two sovereign governments is the non-government sovereign that is the original source of all governmental powers, and that keeps government sovereigns legitimate by connecting them directly to the will and consent of the people. It is the people who retain ultimate supreme sovereign authority over both state and federal governments.185 And indeed the people must have a separate voice—be a separate sovereign—in order to truly give legitimacy to either government. A people who could not disagree with and, if necessary, withdraw their consent from their government is a captured people whose government is certainly not a democracy (and it is not far-fetched to call it a kind of tyranny). In the Tenth Amendment is skepticism of expanding governmental power, both federal and state.
http://cardozolawreview.com/popular-sovereignty-tenth-amendment-reese/