Sovereignty

The supreme, absolute, and independent authority of a state to govern itself and make decisions without external interference. In the U.S. federal system, sovereignty is shared (popular sovereignty, state sovereignty, and federal sovereignty).

Example: The concept of ‘state sovereignty’ was central to the Nullification Crisis and the Civil War, though the post-Civil War constitutional amendments and Supreme Court rulings firmly established that states cannot unilaterally defy federal law.

Common misconception: The United States is a fully sovereign nation in all respects. While the U.S. is a sovereign state under international law, its domestic sovereignty is constitutionally divided between the federal government and the states, meaning neither possesses absolute, unchecked power.

Sources: https://constitution.congress.gov/browse/amendment-10/ — 10th Amendment (Constitution Annotated): reserved powers of the states within the federal system