Why is the ninth month called September?
in U.S. political sense of "a state's refusing to allow a federal law to be enforced," 1798, in Thomas Jefferson; from Late Latin nullificationem (nominative nullificatio) "a making as nothing," from past participle stem of nullificare (see nullify). Related: Nullificationist.
The doctrine that states can set aside federal laws. Urged in the late 1820s by John C. Calhoun, nullification precipitated a crisis between Calhoun and President Andrew Jackson. The doctrine was foreshadowed by Thomas Jefferson's draft of the Kentucky Resolutions. (See Virginia and Kentucky Resolutions.)