Toward the end of the Constitutional Convention, during the debate over the Privileges and Immunities Clause (Article IV, Section 2, Clause 1), Charles Pinckney of South Carolina remarked that “some provision should be included in favor of property in slaves.” The Articles of Confederation contained an extradition clause for escaped criminals, but Pinckney wanted something more specifically directed to the return of slaves. He and his fellow South Carolinian Pierce Butler moved “to require fugitive slaves and servants to be delivered up like criminals.” The motion was withdrawn after James Wilson and Roger Sherman objected, Wilson because the states would be required to track down slaves “at public expense,” and Sherman more pointedly wondered why there was “more propriety in the public seizing and surrendering a slave or servant, than a horse.” The next day, however, the motion was renewed as a formal addition to what would become this clause of Article IV. It passed unanimously and without debate. This was probably because there was a strong precedent in the Northwest Ordinance of 1787 (passed six weeks earlier by Congress), which included a fugitive-slave pro-vision along with its declaration (presaging the Thirteenth Amendment) that “neither slavery nor involuntary servitude” would exist in that territory.

In addition, the English case of Somerset v. Stewart (1772) had concerned Southern slave owners. The master of a fugitive slave from Virginia petitioned for his return. The lord chief justice of the King’s Bench, Lord Mansfield (William Murray), ruled:

The state of slavery is of such a nature that it is incapable of being introduced on any reasons, moral or political, but only by positive law, which preserves its force long after the reasons, occasions, and time itself from whence it was created, is erased from memory. It is so odious, that nothing can be suffered to support it, but positive law. Whatever inconveniences, therefore, may follow from the decision, I cannot say this case is allowed or approved by the law of England; and therefore the black must be discharged.

So the slave was not returned, and news of the case spread through the colonies. The principle that the slave shed his status in a realm free of the positive law of slavery caused alarm in the South. The phrasing of the clause responded directly to Lord Mansfield’s ruling.

Mansfield’s reasoning was grounded in the Western natural law tradition—one held by Chief Justice John Marshall and Justice Joseph Story. Slavery was not a natural condition, but a positive act of law. Indeed, prior to Dred Scott v. Sandford (1857), Missouri law had held that when a master moves a slave into a state prohibiting slavery, the very act “thereby emancipates his slave.” Scott v. Emerson (1852).

A model of circumlocution, the resulting clause is the closest of the so-called Slave Clauses (Article I, Section 2, Clause 3; Article I, Section 9, Clause 1; and Article V) to recognizing slavery as a protected institution. It also became the most controversial of the clauses and was at the center of many constitutional disputes in the 1840s and 1850s.

As initially proposed in the Convention, the language spoke of persons “bound to service or labor” being delivered up to the person “justly claiming their service or labor.” The Committee of Style revised the language to refer to persons “legally held to service or labour” being delivered up to “the party to whom such service or labour may be due,” thereby removing the implication that the claim to the property may be “just.”

At the last moment, the phrase “Person legally held to Service or Labour in one state” was amended to read “Person held to Service or Labour in one state, under the Laws thereof” to make the clause comply, according to James Madison’s notes, “with the wish of some who thought the term legal equivocal, and favoring the idea that slavery was legal in a moral view.” The revision emphasized as well that slaves were held according to the laws of individual states, and that slaveholding was not based either upon natural law or the common law, avoiding the implication that the Constitution itself legally sanctioned the practice. The section also leaves a clear implication, contrary to the holding in Dred Scott v. Sandford, that the slave owner’s property claim did not apply in federal territories, if Congress chose to prohibit slavery there.

Unlike the other three sections of Article IV, Section 2 is written in the passive voice and confers no powers on the federal government. It simply limits state authority, giving rise to the argument that the clause is only declaratory. In 1793, however, Congress passed the Fugitive Slave Act to enforce the clause, but left the mechanism of enforcement primarily with the states. In Prigg v. Pennsylvania (1842), however, Justice Joseph Story effectively nationalized the fugitive slave regime by declaring that a state law that penalized the seizure of fugitive slaves was unconstitutional. Story did note, in an obiter dictum, that the federal government could not compel state officials to enforce the act. This led to numerous states passing personal-liberty laws (prohibiting state officials from enforcing the federal statute).

In one famous case in 1842, Salmon P. Chase (who in 1864 would become chief justice of the Supreme Court) argued that natural law did not recognize the state of slavery and that, on this basis, the 1793 Fugitive Slave Act was unconstitutional. Justice John McLean (who would later dissent in Dred Scott v. Sand-ford), was on circuit presiding over the trial. He firmly rejected Chase’s argument. Chase and co-counsel William Seward took the case to the Supreme Court, which unanimously found against them. Jones v. Van Zandt (1847).

In response to state reluctance to enforce the 1793 act, the South pressed for and gained a new federal Fugitive Slave Act enacted as part of the Compromise of 1850. That act forbade state officials from interfering with the return of slaves. Further, in Moore v. Illinois (1852), the Supreme Court held that states could impose penalties on their citizens for harboring fugitive slaves.

The Fugitive Slave Act of 1850 engendered vigorous popular and legal opposition across the North. Local conventions passed resolutions declaring the act unconstitutional, such as happened in New York and Cleveland. Rescues of slaves who were to be returned caught the public eye in Massachusetts, New York, and Pennsylvania. Juries often refused to convict rescuers. After the Wisconsin Supreme Court set two slave rescuers (John Ryecraft and Sherman Booth) free declaring the Fugitive Slave Act unconstitutional, the United States Supreme Court unanimously reversed the state court in Abelman v. Booth (1859), but the Wisconsin high court refused to acknowledge the decision.

In Dred Scott, Chief Justice Roger B. Taney attempted to use this clause, along with the so-called Migration or Importation Clause (Article I, Section 9, Clause1), as evidence that slaves were not citizens but were to be considered property according to the Constitution. By this clause, Taney argued, “the States pledge themselves to each other to maintain the right of property of the master, by delivering up to him any slave who may have escaped from his service.”

The more generally accepted interpretation, however, is that this clause did not speak to the issue of citizenship at all, but was a necessary accommodation to existing slavery interests in particular states, required for the sake of establishing the Constitution— “scaffolding to the magnificent structure,” Frederick Douglass called it, “to be removed as soon as the building was completed.” This point is underscored by the fact that, although slavery was abolished by constitutional amendment (Thirteenth Amendment), not one word of the original text on the subject had to be amended or deleted.