The drug dealer told me how, acting with the full approval of his cartel, he strolled into the U.S. Immigration and Customs Enforcement (ICE) office for an appointment with federal investigators. He walked through a metal detector and past the portrait of the American president on the wall, then into a room with a one-way mirror. The agents he met were very polite. He was surprised by what they had to say. “One of the ICE agents said they were here to help [the Sinaloa cartel]. And to fuck the Vicente Carrillo cartel. Sorry for the language. That’s exactly what they said.”

So began another small chapter in one of the most secretive aspects of the drug war: an extensive operation by Chapo Guzmán’s forces to manipulate American law enforcement to their own benefit…

Guzmán’s broad strategy has been to knock off rivals and build his own cartel into the dominant criminal force south of the border. One of his tactics for achieving that has been to place his drug-dealing lieutenants as informants for the DEA and ICE. According to sources and court records, he has been carefully feeding intelligence to the Americans. Now, Newsweek has learned, there is a federal investigation into how ICE agents handled some Sinaloa informants near the border.

The implications are sobering: the Sinoloa cartel “is duping U.S. agencies into fighting its enemies,” says Prof. Tony Payan of the University of Texas at El Paso, who studies the cartel wars in Juárez. “Typical counterintelligence stuff. It’s smart. It’s so smart.”