The enactment of the Thirteenth Amendment to the United States Constitution, which abolished slavery except as a punishment for criminal acts, has made the clause mostly irrelevant.
[6]Prior to the American Revolution, there were no generally accepted principles of international law that required sovereign states to return fugitive slaves who had fled to their territory.
After the Three-Fifths Compromise resolved the issue of how to count slaves in the distribution of taxes and the apportionment of the members of the United States House of Representatives, two South Carolina delegates, Charles Pinckney and Pierce Butler, on August 28, 1787, proposed that fugitive slaves should be "delivered up like criminals".
[13][14] If any person bound to service or labor in any of the United States shall escape into another State, he or she shall not be discharged from such service or labor, in consequence of any regulations subsisting in the State to which they escape, but shall be delivered up to the person justly claiming their service or labor.Afterwards, the Convention's Committee on Style formed a digest of the plan, to which many of the delegates later sought to have the word "legally" struck out, fearing this might favor the idea that "slavery was legal in a moral view".
[16] The subsequent passage of the Thirteenth Amendment to the United States Constitution abolished slavery "except as a punishment for crime," rendering the clause mostly moot.
However, it has been noted in connection with the Fugitive Slave Clause that people can still be held to service or labor under limited circumstances; the U.S. Supreme Court stated in United States v. Kozminski, 487 U.S. 931, 943 (1988), that "not all situations in which labor is compelled by physical coercion or force of law violate the Thirteenth Amendment.