What we do know, however, based on the investigation's findings, is that DEA agents not only repeatedly met with Sinaloa heads but did so without bringing Mexican authorities to the table and without tipping off the Mexican government, in clear violation of bilateral agreements. From there:
...the agents of the DEA met with members of the cartels in Mexican territory, to obtain information about their rivals and at the same time establish a network of informants of narco-traffickers, who signed cooperation agreements, subject to results, so that they can obtain future benefits, including charges being dropped in the United States.
That's based on joint, corroborating DEA-DoJ testimony, the first of its kind to be published. The written remarks were provided to a US District Court in Chicago after the arrest of Jesus Vicente Zambada-Niebla, the son of Ismael "El Mayo" Zambada, a Sinaloa boss who reportedly served as the outfit's "logistics coordinator." (In early 2010 when he was extradited to Chicago—a city that scores about 80 percent of its illegal drugs from the Sinaloa—Zambada-Niebla admitted that he was "immune from arrest or prosecution" by virtue of his providing federal US agents with critical intel about Sinaloa rivals.)