ATF says most illegal guns in Mexico come from US Nearly all illegal guns seized in Mexico come from the United States, the head of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives said Monday. ATF acting director Michael Sullivan said investigators have traced 90 to 95 percent of the weapons found in Mexico to the U.S. Generally, only law-enforcement officers or military personnel can legally possess guns in Mexico. Sullivan, speaking at the fifth annual Border Security Conference at the University of Texas at El Paso, said the weapons are being traced as part of an effort by the U.S. and Mexico to stop the illegal flow of guns south. "In Mexico, investigators have provided some tremendous leads ... to weapons trafficking organizations," Sullivan said....