A Fortune investigation finds that the ATF never intentionally allowed guns to fall into the hands of Mexican drug cartels.
FORTUNE -- In the annals of impossible assignments, Dave Voth's ranked high. In 2009 the federal Bureau of Alcohol, Tobacco, Firearms and Explosives promoted Voth to lead Phoenix Group VII, one of seven new ATF groups along the Southwest border tasked with stopping guns from being trafficked into Mexico's vicious drug war.
Some call it the "parade of ants"; others the "river of iron." The Mexican government has estimated that 2,000 weapons are smuggled daily from the U.S. into Mexico. The ATF is hobbled in its effort to stop this flow. No federal statute outlaws firearms trafficking, so agents must build cases using a patchwork of often toothless laws. For six years, due to Beltway politics, the bureau has gone without permanent leadership, neutered in its fight for funding and authority. The National Rifle Association has so successfully opposed a comprehensive electronic database of gun sales that the ATF's congressional appropriation explicitly prohibits establishing one.
Voth, 39, was a good choice for a Sisyphean task. Strapping and sandy-haired, the former Marine is cool-headed and punctilious to a fault. In 2009 the ATF named him outstanding law-enforcement employee of the year for dismantling two violent street gangs in Minneapolis. He was the "hardest working federal agent I've come across," says John Biederman, a sergeant with the Minneapolis Police Department. But as Voth left to become the group supervisor of Phoenix Group VII, a friend warned him: "You're destined to fail."
Voth's mandate was to stop gun traffickers in Arizona, the state ranked by the gun-control advocacy group Legal Community Against Violence as having the nation's "weakest gun violence prevention laws." Just 200 miles from Mexico, which prohibits gun sales, the Phoenix area is home to 853 federally licensed firearms dealers. Billboards advertise volume discounts for multiple purchases.
Customers can legally buy as many weapons as they want in Arizona as long as they're 18 or older and pass a criminal background check. There are no waiting periods and no need for permits, and buyers are allowed to resell the guns. "In Arizona," says Voth, "someone buying three guns is like someone buying a sandwich."