The Nullification Crisis was a constitutional debate over the authority of states to declare an act of Congress unconstitutional. The primary issue was the Tariff of 1828, despised in the South and known there as the "Tariff of Abominations."
John C. Calhoun, who had been Vice President under Andrew Jackson anonymously wrote a treatise known as the South Carolina Exposition and Protest. The Exposition argued that a state could call a convention which had the power to declare acts of Congress null and void within its borders; and such a declaration would be binding on both the state and federal governments. In 1833, South Carolina convened such a convention and declared the Tariffs of 1828 and 1832 null and void within its borders. This drew a furious reaction from President Andrew Jackson who threatened to send troops to South Carolina, and also to hang Calhoun. On December 10, 1833, Jackson issued his famous Nullification Proclamation in which he said that nullification was:
incompatible with the existence of the Union, contradicted expressly by the letter of the constitution, unauthorized by its spirit, inconsistent with every principle for which it was founded, and destructive of the great object for which it was formed....
The laws of the United States must be executed....Those who told you that you might peaceably prevent their execution deceived you; they could not have been deceived themselves....Their object is disunion.
Jackson sent troops under General Winfield Scott to enforce the Tariff, and armed resistance seemed imminent; however Henry Clay offered a compromise which offered lower tariffs and both sides backed away claiming victory. The Nullification Crisis was an indication of things to come, namely the Civil War. John C. Calhoun soon retired after the controversy, but commented from his home:
The Struggle, so far from being over, is not more than fairly commenced.