In international law, sovereignty is a key concept referring to the exercise of power by a state. De jure sovereignty is the legal right to do so; de facto sovereignty the ability in fact to do so (which is especially of concern upon the failure of the usual expectation that de jure and de facto sovereignty exist at the place and time of concern, and rest in the same organization).

(A monarch, who rules a sovereign country, is also called a sovereign; the idea which that case and the subject of this article have in common is that of supremacy within the geographic boundaries of that sovereignty, in contrast to any obligation to defer to a higher authority.)

Tribal sovereignty refers to the right of federally recognized American Indian nations or tribes to exercise limited jurisdiction within and sometimes beyond reservation boundaries.

Sovereignty and Federalism

The question whether the individual states of the Union remained sovereign was debated in USA:

• According to the theory of J. C. Calhoun, the states had entered into an agreement from which they might withdraw if its terms were broken, and they were sovereign.

• According to the theory expounded in the Federalist party, the individual states did not, after the formation of the constitution, remain completely sovereign: they were left in possession of certain attributes of sovereignty, while others were lodged in the Federal government; while there existed many states, there was but one sovereign. Even if the origin was a compact or contract, after the "United States" were formed by a "constitutional act" there no longer existed a mere contractual relation: there existed a state to which all were subject, and which all must obey.

• According to Austin: In the case of a composite state or a supreme federal government, the several united governments of the several united societies together with a government common to these several societies, are jointly sovereign in each of these several societies and also in the larger society arising from the federal union, the several governments of the several united societies are jointly sovereign in each and all.