The ruling reconfirmed the Ker-Frisbie Doctrine, established in Ker v. Illinois (1886) and Frisbie v. Collins (1952), which generally permits the prosecution of criminal defendants regardless of whether their presence was obtained in accordance with an applicable extradition treaty.

Humberto Álvarez Machaín, a Mexican physician, was allegedly involved in the 1985 kidnapping, torture, and murder of Enrique Camarena Salazar, an American citizen employed by the U.S. Drug Enforcement Agency, by "prolonging [his] life so that others could further torture and interrogate him."

On April 2, 1990, Álvarez was abducted from Mexico by Trent Tompkins, a U.S. citizen hired by DEA agents, and brought to trial in the United States over the protest of Mexican officials.

Despite vigorous protests from the Mexican government, Álvarez was tried in United States District Court in Los Angeles; the trial, in which his defense focused intensely on the legality of the arrest, resulted in an acquittal.

The trial judge (whose earlier decision dismissing the indictment had been overruled by the Supreme Court) ruled at the close of the government's case in chief that the government had not presented a prima facie case, and therefore granted an acquittal without presenting the matter to the jury for verdict.