Toward the end of the Constitutional Convention, after previous clauses concerning slavery had been settled, and in the midst of the discussion about the process of amending the Constitution, John Rutledge of South Carolina declared that “he never could agree to give a power by which the articles relating to slaves might be altered by the States not interested in that property and prejudiced against it.” An addition to the clause was immediately agreed to that forbade amending the Migration or Importation Clause (Article I, Section 9, Clause 1) and the Direct Taxes Clause (Article I, Section 9, Clause 4) prior to 1808, after which Congress could regulate the slave trade.

This provision calls attention to the delicacy and precariousness of the compromises involved in these two clauses. Even though only a few states had begun to move toward abolition or gradual emancipation at the time, the tide of anti-slavery opinion seemed so strong as to excite the demands of Georgia and South Carolina in particular to preserve the institution at least within their own states. Taking a mid-summer break from the convention and knowing Southern opinion on the matter, Alexander Hamilton—without breaking his pledge of secrecy—prevailed upon John Jay and the New York Manumission Society not to submit a proposed petition to the Constitutional Convention to abolish slavery. At Hamilton’s request, Jay even destroyed his draft of the petition.

Protecting the slave trade in the Migration or Importation Clause revealed Southern concerns about the strength of antislavery opinion (which was at that time focused on stopping the slave trade). In fact, in 1787, only North Carolina and Georgia permitted the importation of slaves, and so the slave states thought that it might be difficult to prevent a coalition of Northern and upper Southern states from changing the Constitution on this question by amendment. Likewise, shielding the Direct Taxes Clause was an indirect way to emphasize the “Three-fifths Compromise” (Article I, Section 2, Clause 3) concerning the apportionment of direct taxes, as well as adding “other taxes” to that ratio, reflecting significant fears that the power to tax could be used to undermine the institution of slavery. Earlier, Gouverneur Morris, the most outspoken opponent of slavery at the convention, nonetheless conceded that “he did not believe that those [southern] States would ever confederate on terms that would deprive them of that trade.”

Underscoring the temporary nature of the compromise, language in Article V ties the Direct Taxes Clause to this clause’s “implied invitation” to legislate on the slave trade after 1808. By that time, the internal production of slaves would be sufficient to supply the growing market so that economic self-interest did not stand in the way of legislation based on the moral revulsion to the slave trade. Congress accepted the invitation, and although the law underwent several modifications in subsequent years, on March 2, 1807, it passed a federal prohibition of the slave trade, effective January 1, 1808. The vote in the Senate had been eighteen to nine (with seven abstentions) and, in the House, 113 to five (with twenty-two not voting). A few weeks later, on March 25, 1807, following decades of agitation by William Wilberforce, the British Parliament also banned the trade.

Interestingly, reference to the Fugitive Slave Clause (Article IV, Section 2, Clause 3) is not included here among the clauses protected from amendment. The omission signifies the broad consensus supporting the Fugitive Slave Clause and the fact that it was not at the time thought to be controversial.