The Slavers case was a landmark decision by the United States Supreme Court in 1864. It involved two ships, the Sarah and the Wildfire, which were seized by Union forces during the Civil War for transporting slaves from Africa to Cuba. The owners of both vessels argued that they had not violated any laws because slavery was legal in Cuba at that time. However, Chief Justice Salmon P. Chase wrote an opinion for a unanimous court ruling against them on grounds that international law prohibited slave trading regardless of local statutes or customs. He also noted that even if it had been permissible under Cuban law, it would still have been illegal under American federal statute since Congress had outlawed such activity years before with its passage of the Slave Trade Act of 1820. This ruling established an important precedent regarding human rights and helped pave the way towards eventual emancipation and freedom for all enslaved people in America

In The Slavers, the Supreme Court was tasked with determining whether a vessel and its cargo were subject to condemnation as prize of war. The majority opinion held that the vessel and its cargo should be condemned because it had been used for illegal slave trading in violation of international law. However, Justice Nelson dissented from this decision on two grounds: firstly, he argued that there was no evidence presented at trial showing that the vessel or its owners knew about or intended to engage in any illegal activity; secondly, he asserted that even if they did know about such activities, their actions would not constitute an offense under international law since slavery itself is not prohibited by any treaty between nations. He concluded his dissent by stating "the court has gone beyond what can be justified upon principle."