In 1820, the U. S. Navy commissioned schooner Alligator intercepted La Jeune Eugénie, a French-flagged slave ship built in the United States, off the coast of West Africa.
Brought to Boston for adjudication, the case presented an explosive legal question: could an American federal court confiscate a foreign vessel engaged in the slave trade if that trade was illegal under the vessel's home nation laws? Presiding over the U. S.
Circuit Court for the District of Massachusetts, Supreme Court Justice Joseph Story issued a groundbreaking opinion in 1822. Story ruled that the international slave trade violated the fundamental law of nations, natural ethics, and universal moral principles. By equating human trafficking at sea with maritime piracy, Story asserted that slavers were hostes humani generis—enemies of all mankind—and therefore subject to universal jurisdiction by any nation's Admiralty courts.
This bold ruling sought to establish a precedent where U. S. courts could enforce global abolition by treating slave traders as common pirates regardless of national flags.
However, the decision created an immediate geopolitical crisis. The French government strongly protested the ruling as an infringement on foreign sovereignty, and the Monroe administration feared diplomatic fallout. Just three years later, in the 1825 case The Antelope, Chief Justice John Marshall effectively overturned Story's legal doctrine.
Marshall ruled that while the slave trade was abhorrent, it was permitted under the positive law of nations if a sovereign state allowed it, thereby prioritizing national sovereignty over universal moral law. Justice Story's attempt to weaponize maritime law against human trafficking remains a pivotal moment in global human rights law.