Act Prohibiting Importation of Slaves Signed After Constitutional 20-Year Protection Expires

President Thomas Jefferson signs into law the Act Prohibiting Importation of Slaves (2 Stat. 426), passed by Congress on March 2, 1807, prohibiting the importation of enslaved people into the United States effective January 1, 1808—the earliest date permitted by the Constitution’s Article I, Section 9, Clause 1. Jefferson promotes this legislation in his December 2, 1806 State of Union Address, calling for criminalization of the “violations of human rights” attending the international slave trade. Under Representative Joseph Bradley Varnum’s leadership, the bill moves through Congress and both houses agree on final language imposing heavy penalties on international slave traders. The Act represents the culmination of Jefferson’s decades-long advocacy for ending slave importation, which he promoted since the 1770s, and demonstrates that ending the constitutional 20-year protection period enables federal action against the Atlantic slave trade.

The 1807 Act marks a significant shift from the 1794 Slave Trade Act which merely prohibited American ships from participating in the international trade—the new law criminalizes all importation from abroad even on foreign ships, attempting comprehensive closure of the slave trade. Congress gives slave traders nine months’ notice by passing the law in March 1807 for a January 1, 1808 effective date, allowing operations to wind down. The legislation imposes substantial penalties on violators, and an 1819 Act later declares slave importation “piracy” punishable by death or arrest, demonstrating escalating federal commitment to enforcement. The Act fulfills James Madison’s 1788 prediction in Federalist No. 42 that the twenty-year constitutional protection was “a great point gained in favor of humanity that a period of twenty years may terminate forever” what he called an “unnatural traffic.”

However, the Act’s passage reveals the profound corruption embedded in the Constitution’s 1787 slave trade protection clause: the twenty-year guaranteed access to African captives enables an estimated 170,000 additional people to be forcibly imported into American slavery between 1788 and 1808—human trafficking constitutionally protected by founding elites prioritizing southern economic interests and Union preservation over human rights. While the 1807 Act ends legal international slave trade, it does not end slavery itself or the domestic slave trade, which flourishes for another 58 years. Illegal smuggling continues despite the law, demonstrating limited federal enforcement capacity and continued demand for enslaved labor. The Act exemplifies how constitutional corruption operates: elite slaveholders successfully embedded 20-year trade protection in 1787, profited from two decades of human trafficking, and only faced federal prohibition when the constitutional deadline they themselves negotiated finally arrived. The domestic slave trade and slavery’s westward expansion continue unabated, showing that ending importation merely shifts the source of enslaved people from Africa to American breeding and internal trafficking.