Alvarez-Machain (Alvarez) (plaintiff) alleged he was wrongfully captured and arbitrarily detained in Mexico by Sosa (defendant), a bounty hunter operating as a United States agent. The operation to capture and detain Alvarez was planned and directed by Drug Enforcement Administration (DEA) agents in the United States. After Alvarez was captured in Mexico, he was brought to the United States to be tried for the murder of a DEA agent. After Alvarez's acquittal, he sued the United States for false arrest under the Federal Tort Claims Act (FTCA), which waives the government's sovereign immunity in some circumstances and allows the government to be sued in a tort action. Alvarez also brought suit against Sosa under the Alien Tort Statute (ATS), which gives federal district courts original jurisdiction over an alien's civil action for a tort committed in violation of the law of nations or a U.S. treaty. Alvarez alleged that Sosa violated the United Nations Universal Declaration of Human Rights (Declaration), the International Covenant on Civil and Political Rights (Covenant), and customary international law by arbitrarily detaining him. The district court awarded Alvarez summary judgment and damages on his ATS claim against Sosa and dismissed Alvarez's FTCA claim against the United States. The appellate court affirmed the judgment on Alvarez's ATS claim and reversed the dismissal of Alvarez's FTCA claim. The United States Supreme Court granted certiorari.