What is the principle of nullification in U.S. law?

The principle of nullification in U.S. law refers specifically to the idea that states have the authority to invalidate federal laws that they believe are unconstitutional. This concept emerged in the early 19th century and was notably articulated during the debates surrounding the Alien and Sedition Acts and later became associated with the South's response to federal laws they deemed unfavorable, particularly during the nullification crisis in the 1830s.

The historical context of nullification rests on the belief that the states have the right to interpret the Constitution and assess the legitimacy of federal actions. While this principle has been largely rejected by the Supreme Court, which upheld the supremacy clause of the Constitution, nullification has influenced debates about states' rights and federal power throughout American history.

Other options, such as states declaring war, creating their own currency, or seceding, do not align with the established legal framework of U.S. governance. The Constitution explicitly grants Congress the authority to declare war and regulate currency, while the legality of secession was ultimately addressed during the Civil War and reaffirmed by the Supreme Court in later rulings. Thus, the correct understanding of nullification is firmly encapsulated in the notion that states can declare federal laws unconstitutional.