The 1807 act was a comprehensive attempt to close the slave trade. By passing the law in March, Congress gave all slave traders nine months to close down their operations in the United States.
The ten sections of the 1807 act were designed to eliminate all American participation in the trade. Section 1 set the tone. After January 1, 1808, it would "not be lawful to import or bring into the United States or the territories thereof from any foreign kingdom, place, or country, any negro, mulatto, or person of colour, with intent to hold, sell, or dispose of such [person] ... as a slave, to be held to service or labour." The act provided an enormous penalty up to $20,000 for anyone building a ship for the trade or fitting out an existing ship to be used in the trade.
Penalties for participating in the trade varied. American citizens were subject to fines of up to $10,000 and jail terms of no less than five years and no more than ten years. Ships of any nation found in American ports or hovering off the American coast with Africans on them could be seized and forfeited, with the captain facing a $10,000 fine and up to four years in prison. Any American who purchased an illegally imported slave would lose that slave and be fined $8,000 for every one purchased. The law allowed the United States Navy to interdict ships involved in the illegal trade. It also required ships legally transporting slaves from one part of the nation to another (the domestic slave trade remained legal until 1865) to register their passengers with port authorities before commencing their voyage.
The law certainly had teeth to it. Fines under the statute were enormous, and the potential jail time was surely enough to discourage most slave smugglers. Moreover, for the Jefferson administration, which never much liked federal power, this act constituted a huge grant of power to the national government. Had Congress provided sufficient funding to enforce the law, it would surely have closed the trade. Funding would, however, be problematic until the Civil War.
There was one other problem with the 1808 law: the fate of the illegally introduced slaves. Logically, they should have been either freed in the United States or sent back to Africa. After all, one of the goals of the law was to end the importation of new slaves from Africa. But given the views of President Jefferson, and many of the leaders of his party, either option was impossible. Jefferson was deeply hostile to the presence of free blacks. In a letter to Edward Coles, shortly after he left office, he referred to them as "pests" in society. Thus, his administration had no interest in freeing Africans who were illegally introduced into the nation. Nor was the deeply parsimonious Jefferson likely to support spending any money on returning them to their homelands. They may have been illegally seized and illegally brought to America, but that did not mean they should be free.
Reflecting Jefferson's ideology of states' rights, his hatred of free blacks, and his refusal to spend money unless absolutely necessary, the law provided that slaves illegally found in the United States would be treated according to the law of the state in which they were found — or brought to. In practice, this meant they would become slaves in the United States, and that the states would profit by selling them.
Under the law the United States would make money from the sale of confiscated ships and the large fines imposed on anyone involved in the trade. People informing on those who violated the law, as well as the crews of naval ships that seized traders, would also share in the proceeds from the sale of the seized ships. Southern states would get money from the sale of illegally imported slaves, and southerners would have access to more slaves. Anticipating the logic of Chief Justice Roger B. Taney's decision in Dred Scott v. Sandford (1857), the Africans themselves would "have no rights," and remain slaves. In sum, the act of 1807 provided heavy penalties great disincentives for slave traders, but ignored the slaves themselves. They were treated like merchandise to be transferred from the smuggler to some owner who could get a clear title to them. The 1807 act sought to end the trade, but did nothing to undermine the legitimacy holding men and women in bondage. In that respect, it truly represented the ideology of the president who signed it into law.