A legislature may nullify a ban, a law, or a tax by simply passing a new law. Election results can be nullified if a court finds the voting process was improper, and a court ruling can be nullified by a higher court. Even the Supreme Court itself may have its decisions nullified by new laws passed by the Congress—though not if a decision is based on the Constitution. In the years leading up to the American Civil War, Southern states claimed the right to nullify any federal law (such as antislavery laws) that they believed to be unconstitutional, leading to the Nullification Crisis of 1832. Annul is a close synonym of nullify (with the same root), as are abrogate and invalidate.