Importing slaves was also illeagle In the U.S. long befor the chantey was popular. however the practice did continue into the mid 19th century. I would also like to comment on the Amistad. Although not a bad movie it's very misleading. The Amistad was not involved in the slve trade at all as far as current research has been able to uncover. She was a coasting schooner employed in carrying cargo on the coast of Cuba. On the voyage in question Her cargo happened to be captive people, with papers stating that they were Cuban natives. As it was also illegal for spanish colonies to import. The captives did revolt, were capture and tried for murder & piracy. The U.S. courts eventually fond them to be infact not Cubans. And subsequently judged them to be kidnapped And acting in self defense.