Nullification is the legal theory that a state has the right to invalidate any federal law that it deems unconstitutional. This concept emerged in the early 19th century, particularly associated with the Nullification Crisis in 1832 when South Carolina attempted to nullify federal tariffs. Proponents argue that states have a sovereign authority to interpret the Constitution, while opponents contend that such actions undermine federal authority and the unity of the nation. Ultimately, nullification has been largely rejected by the courts and federal government.