The Supreme Court's ruling in United States v. Álvarez-Machaín centered on the extradition of a Mexican physician, Humberto Álvarez-Machaín, who was accused of facilitating the kidnapping and murder of a U.S. Drug Enforcement Administration (DEA) agent in Mexico. The case arose when U.S. agents, without permission from the Mexican government, abducted Álvarez-Machaín from Mexico and brought him to the United States to face trial. The legal question was whether such an act was permissible under U.S. law and in line with international practices regarding extradition. The Court ruled that U.S. law permits the government to engage in forcible abduction if the foreign government does not comply with requested extradition procedures, thus endorsing a controversial approach to law enforcement across borders.

The Court’s decision sparked a significant debate over international sovereignty and the rights of foreign nations. The justices' majority opinion emphasized that since Mexico's extradition treaty with the U.S. did not explicitly prohibit such actions, the U.S. government held authority to apprehend individuals accused of crimes, even in foreign territories. This ruling reinforced a broader application of U.S. jurisdiction and highlighted the complexity of international law concerning law enforcement cooperation. Ultimately, this case underscored the tension between U.S. judicial actions and foreign sovereignty, continuing a trend in which U.S. authorities assert the right to intervene in the affairs of other nations when deemed necessary for law enforcement.