What is dual sovereignty in the U.S. federal system?

In the U.S. federal system, the concept of dual sovereignty refers to the division of governing authority between the national government and the individual states. Unlike systems where sovereignty is vested in a single, supreme legislative body, the American structure is defined by a federal union where powers are constitutionally distributed.12

This arrangement arises because the Constitution of the United States does not grant the national legislature absolute power; instead, it imposes specific restrictions and reserves all powers not delegated to the federal government—or prohibited to the states—to the states themselves or to the people, as outlined in the Tenth Amendment.1

Because the Constitution serves as the fundamental law, sovereignty is often viewed as residing in the document itself or in the people, who may exercise their authority through both federal and state levels. This functional division provides a territorial separation of powers, which acts as a restraint against the abuse of governmental authority and allows states to function as "laboratories of democracy".13