The flow of guns from the U.S. to Mexico shares some DNA with the black market drug trade between the two countries. "Firearms that criminal organizations acquire from the United States are primarily transported overland into Mexico using the same routes and methods employed when smuggling bulk cash south and drugs north across the U.S.-Mexico border," the report notes.
Typically, it appears that criminal organizations in Mexico rely on straw purchases in the United States to acquire guns legally and then funnel them southward. "Firearm trafficking organizations also frequently obtain firearms from unlicensed private sellers in secondary markets, particularly at gun shows and flea markets or through classified ads or private-party Internet postings," the report found.
A 2013 University of San Diego report found that nationally, the illegal firearms trade with Mexico accounted for $127 million in annual revenue for the U.S. firearms industry, or 2.2 percent of all gun sales. For certain sellers along the border, this percentage is likely to be much higher.
The Bureau of Alcohol, Tobacco and Firearms has data on exactly which of these retailers are disproportionately likely to sell guns that end up in the hands of cartels. But neither you nor I nor researchers nor state and local governments are allowed to see that data thanks to Congress. In 2005, they passed a bill prohibiting ATF from sharing this data with the public, government agencies, and even with researchers who could help figure out how to try to stanch the flow of illegal guns.
But we do know that in aggregate, among the guns that could be traced back to a particular dealer, nearly three-quarters originated from a seller in California, Arizona or Texas, according to the GAO report. The report notes that there are thousands of licensed firearm dealers operating in those states. And this map, created from ATF data by online mapmaker MetricMaps, shows that there are over 730 licensed firearm sellers, including pawn shops dealing in firearms, just in the counties along the U.S.-Mexico border.
There are any number of steps authorities could take to reduce the southward flow of guns. President Obama's recent executive actions on guns, which will require more sellers to obtain a federal firearms license, may be helpful to the extent that they increase background checks for gun purchases along the border. Open access to the data on who, exactly, is selling these guns is another potential way to address the issue, but that would require an act of Congress.
And several years ago, ATF implemented a rule requiring dealers in the border states to report multiple sales of certain high-caliber rifles to the ATF. Gun rights groups like the NRA called "foul." The NRA backed a lawsuit to get the rule overturned, but it in 2013 a three-judge federal panel ruled unanimously that it could stay in place.
ATF reports that the rule is working. "ATF officials reported that this information has helped them identify firearms traffickers and others involved in a timelier manner, which on several occasions has led to arrests and seizures of firearms intended for trafficking to Mexico," according to the GAO report. The number of American-made rifles seized by Mexican authorities has fallen by more than half since the rule was implemented in 2011.
The gun debate in this country is often framed between extremes -- either you take people's guns away, or you don't do anything. But the ATF reporting requirement is just one example of a minor regulatory change between those extremes that can have a real-world impact on gun violence.