The Slavers case was a landmark decision by the United States Supreme Court that held that slavery is illegal in all states. The case involved two ships, the Weathergage and the Wildfire, which were seized by Union forces during the Civil War for transporting slaves from Africa to Cuba. The owners of these vessels argued that they had not violated any laws since their actions took place before Congress passed legislation banning slave trade with foreign countries. However, Chief Justice Salmon P Chase wrote an opinion stating that even though no law existed at the time of their voyage prohibiting such activities, it was still against public policy and therefore illegal under international law. He further stated that this prohibition applied to both domestic and foreign commerce involving slaves or persons held as slaves regardless of when it occurred. This ruling established a precedent for future cases regarding slavery in America and set forth clear guidelines on what constituted unlawful activity related to human trafficking across state lines or internationally.

In The Slavers case, the Supreme Court was asked to decide whether a ship seized by the United States Navy during the Civil War could be considered a "prize of war" and therefore subject to confiscation. Chief Justice Chase delivered an opinion for the majority which held that it could not be so classified because it had been captured in violation of international law. However, Justice Nelson dissented from this decision arguing that since Congress had authorized such seizures as part of its wartime powers, they should be allowed under existing laws. He argued further that even if there were some violations of international law involved in capturing these vessels, they still fell within Congress' authority to declare prizes and thus should not have been excluded from consideration as such.