A highly trusted former deputy attorney general, who later became Mexico’s drug czar and was embraced by Washington until his death, is accused in a U.S. Drug Enforcement Administration report of taking bribes from one of Mexico’s oldest narcotics trafficking cartels. Jose Luis Santiago Vasconcelos, killed in November in a mysterious plane crash over Mexico City, is among three senior federal law-enforcement officials named in an April 21-page DEA briefing on organized crime and drug trafficking south of the border. Vasconcelos was never charged with a crime. The other two are being prosecuted by Mexico. The report, prepared as a...