Short of secession, nullification is the most extreme position of the states' rights philosophy. It is based upon the belief that the Union was a voluntary joining of sovereign states and that those states had the right to nullify, or invalidate, within their boundaries any unconstitutional actions of the federal government. This view is an extension of Jefferson's belief in the supremacy of individual and states' rights over federal governmental powers. The nullification concept was first raised by the Virginia and Kentucky Resolutions in 1798-99 in reaction to the Alien and Sedition Acts. In 1809-10 nullification was briefly revived by New England states which opposed a national embargo (Non-Intercourse Act). The concept returned in Southern reactions to the Tariff of 1828, the Tariff of 1832 and the accompanying contest involving John C. Calhoun, Daniel Webster, Henry Clay and Andrew Jackson. In 1861 South Carolina and other Southern states attempted the ultimate in nullification in the Secession Crisis.