The Slavers case was a decision by the United States Supreme Court in 1864. The case involved two ships, the Kate and the Wildfire, which were used to transport slaves from Africa to Cuba. The owners of these vessels argued that they had not violated any laws since slavery was legal in Cuba at the time. However, Chief Justice Salmon P. Chase ruled against them on behalf of a majority opinion stating that transporting slaves between countries is illegal under international law regardless of whether or not it is legal within those countries themselves. This ruling established an important precedent for future cases involving human trafficking as well as other forms of international commerce and trade law violations. It also set forth clear guidelines regarding what constitutes an illegal act when dealing with foreign nations and their citizens or goods crossing borders without proper authorization from both governments involved in such transactions

In The Slavers, the Supreme Court was asked to decide whether a slave-trading vessel captured by the United States Navy and brought into port could be considered a "pirate" under international law. The majority opinion held that it could not, as piracy requires an intent to commit robbery or other criminal acts on the high seas. However, in his dissenting opinion Justice Grier argued that slavery itself is a crime against humanity and should therefore qualify as piracy regardless of any specific intent to rob or steal from others. He further noted that even if this were not true, there was sufficient evidence presented at trial for the jury to find beyond reasonable doubt that those aboard had intended to engage in illegal activities such as kidnapping and transporting slaves across international borders without proper documentation. As such, he concluded that they should have been found guilty of piracy under both domestic and international law.