In March 2015, BBC TV programme "This World" broadcast an episode entitled "Secrets of Mexico's Drug War" which reported on the US government's Bureau of Alcohol, Tobacco, Firearms and Explosives' Operation Fast and Furious which had allowed licensed firearms dealers to sell weapons to illegal buyers acting on behalf of Mexican drug cartel leaders, in particular the Sinaloa Cartel. The BBC also reported on Vicente Zambada Niebla's claims of immunity from prosecution under a deal between the Mexican and US governments and his claims that the Sinaloa Cartel's leaders had provided US federal agents with information about rival Mexican drug gangs. In the same documentary it is shown that the US Justice Department invoked national security reasons to prevent Humberto Loya Castro, the lawyer of the Sinaloa Syndicate, from being summoned as a witness to the trial against Vicente Zambada Niebla.