Read the excerpt below and then answer the following question. It is also a most important consideration in the present case, which ought not to be lost sight of, that, supposing these African negroes not to be slaves, but kidnapped, and free negroes, the treaty with Spain cannot be obligatory upon them; and the United States are bound to respect their rights as much as those of Spanish subjects. U. S. Supreme Court opinion, 18414 This opinion most likely refers to which of the following events from the abolition movement?