The Spanish government had put forward certain demands to the United States even before the Hartford trial. The Spanish Minister, de la Barca, wrote to the Secretary of State, John Forsyth, a former Minister to Spain and a known defender of Negro slavery, that when the Amistad was " rescued," she should have been set free to return to Cuba so that the Africans on board could have been "tried by the proper tribunal, and by the violated laws of the country of which they are subjects." This had not been done, and so he put forward a further set of demands. He claimed the vessel and cargo, including the Africans, in the name of the Spanish Monarch, demanding that they be sent back to Havana for adjudication, since "no tribunal in the United States has the right to institute proceedings against, or to impose penalties upon, the subjects of Spain, for crimes committed on board a Spanish vessel, and in waters of the Spanish territory." He cited articles of existing treaties between the United States and Spain to buttress his case.

The U.S. President, Martin Van Buren, had no strong views on the slavery question, but he depended on the support of the Southern pro-slavery Democrats, whose goodwill he wished to maintain for the upcoming presidential election in 1840. He, therefore, told Forsyth on September 11 to instruct District Attorney William S. Holabird to "take care that no proceedings of your Circuit Court, or any other judicial tribunal, place the vessel, cargo, or slaves beyond the control of the Federal Executive." The President hoped that the courts would order the Amistad captives returned to Cuba, thus relieving him of political pressure from both the Southern Democrats and the Spanish government; but he was prepared to return the captives on his own authority, if necessary. To bolster support for such a potential move and to placate the Spanish, he requested an opinion from U.S. Attorney General Felix Grundy, who declared that the Africans were to be considered the property of those for whom the Spanish Minister was claiming them, and that the ship should be returned with all its contents to Cuba. The Cabinet endorsed this view.