The decision to include an enforcement clause stemmed from an oversight in the Northwest Ordinance of 1787, which every student of AP United States history knows barred slavery from the territories north of the Ohio River. While it succeeded in pushing out many slaveholders from the region, those who stayed soon learned that the ordinance had no teeth. It could not be enforced. In fact, at one time slaveholders occupied the governor’s chairs in the new states of Illinois and Indiana. In 1820, census takers counted 917 slaves in Illinois and 190 in Indiana. It took another 25 years for Illinois to comply with the terms of the Northwest Ordinance. Diehard Confederate resistance no doubt convinced Republican authors of the 13th Amendment that the defeated slave states would only comply with a constitutional amendment ending slavery if it came with an explicit enforcement clause.
But what authority did Congress give itself to enforce the 13th Amendment? Was it to be interpreted broadly or narrowly, and did it extend beyond simply ensuring that former slaves were not being bought or sold to include full civil rights? These questions were hotly debated by state legislatures between February and December 1865.
Strong Republican states that awarded President Abraham Lincoln with a second term in office in 1864 voted overwhelmingly for the amendment in the first weeks of February. The first signs of trouble occurred in the “Border States” of Delaware and Kentucky as well as New Jersey. Delaware was one of four Border slave states that remained in the Union, and its slave population amounted to no more than 1,200. But Democrats in the state legislature weren’t concerned about abolition. Their worries centered around how the federal government might interpret the provisions of the enforcement clause and based on that interpretation, just what the government might then force the states to do beyond ratifying an amendment ending slavery. Gov. Gove Saulsbury spoke for many in his state when he argued that the "Black Republicans" would next "demand for the negro the right of suffrage, and seek to place him, politically at least, upon an equal with the white man." Shortly thereafter, the amendment came up for debate for the second time in Kentucky, where not even a provision calling for federal compensation to slaveholders and the removal of every black person could marshal sufficient support.