Cartels are bringing assault rifles and other weapons into Mexico through a robust underground supply chain, capitalizing on their proximity to the United States’ $21 billion gun and ammunition manufacturing industry and the relatively loose restrictions on weapons purchasing.

With roughly 70% of Mexico’s guns coming from the United States, the flow of weapons southbound is empowering the same organizations that smuggle drugs and migrants north across the U.S. border. These groups rely on guns to maintain their trade routes and defend themselves against Mexico’s military and police forces. 

For years, these powerful criminal organizations have developed supply chains — often originating in the United States — to arm their networks. Once small-time operations that moved a couple of guns at a time, in recent years the trade has become more sophisticated, said Craig Larrabee, special agent in charge for Homeland Security Investigations in San Antonio.  

“We’re seeing larger loads of firearms being smuggled at one time,” he said, with upwards of 250 weapons in a single load. “It’s indicative of more of an organizational approach to the firearm smuggling.”

Since 2020, the U.S. has ramped up efforts to crack down on the southward flow of arms, but major challenges persist in shutting down this well-oiled operation. It relies heavily on straw purchasers — often U.S. citizens without a criminal record who will make an initial gun purchase on behalf of a criminal organization. 

“You’ll have somebody make a purchase from a federal firearms licensee, like a gun shop, or a gun show or a person-to-person sale,” Larrabee said. The weapons often cost several thousands of dollars.

Then the guns are usually taken to a stash house, which could be a residence or a storage unit. From there, another person will pick up the weapons and hide them in a vehicle.

“Then they’ll be smuggled across and sent to the purchaser down in Mexico,” Larrabee said.

This is happening as the administration in Washington faces mounting political pressure to better control what and who crosses the border. U.S. agencies are collaborating more closely with one another and with officials in Mexico to better track the use of these guns and their path from U.S. localities to sites across the border. And under the Bipartisan Safer Communities Act, the U.S. upped penalties for arms trafficking and straw purchasing of guns for people not authorized to have them.

Earlier in October, top U.S. officials touted their efforts at a bilateral security summit in Mexico City. 

“Just last month, we charged and arrested seven defendants in Texas for buying over 100 guns later trafficked to Mexico,” said U.S. Attorney General Merrick Garland. 

Also at the summit, Secretary of Homeland Security Alejandro Mayorkas said firearms interdiction has increased 44% in the last year. Southbound arms enforcement statistics for fiscal year 2023 have yet to be made public. 

But officials set on stemming the southward flow of guns face a number of challenges, including corruption in Mexico, limited agency capacity, gaps in data sharing and inadequate data quality, according to Mark Ungar with City University of New York. 

“The data from the states in Mexico is very poor, it’s very corrupted,” he said. “And there’s no powerful capacity or political will, at the national level in Mexico, to hold those states accountable.”

He said authorities also lack understanding of the scope of this massive global supply chain, especially as criminal groups in different countries increasingly work together to move weapons.

“By focusing on the U.S.-Mexico border, they’re getting the hotspot nexus of where that really counts,” he said. “But that’s only part of this larger picture of the flow of weapons.” 

And the U.S. continues to make a healthy supply of guns available to nefarious parties.

Research firm IBISWorld expects the U.S. arms and ammunition manufacturing industry to grow over the next five years. The continued prevalence of gun shows, with thousands held each year across the country, will also facilitate the flow of weapons to Mexico, according to Rice University professor Tony Payan.

“It’s almost impossible for the bureaucracy to also keep track of all these guns, and all these shows, and all these sales, and all these private transactions,” he said.

“Mexico is not really a producer of guns. It’s got very strict gun regulations. And so most guns can be traced back to the United States,” he said.

With that access to guns, cartels can continue to run their underground businesses, said Craig Larrabee of Homeland Security.

“They control their routes through firearms,” he said. “It’s vital for their ability to stay in power and control those areas for the smuggling of people, for their smuggling of narcotics, for the extortion schemes, for all the different things that they do to terrorize communities in Mexico.” 

For Josefina De León, it was cartel violence that forced her to flee her home in the northern Mexican state of Tamaulipas. She’s been an advocate for crime victims since her daughter went missing there more than 10 years ago, and she’s watched gun violence increase.

“It’s easy for people to obtain guns,” De León said in Spanish.

Despite Mexico’s strict gun laws for civilians, the bloodshed has worsened, she said — and not just at the hands of cartels. Firearms are also being used at home, such as in cases of domestic violence.

“It’s a major industry, with many interests,” she said, “where it doesn’t matter if people die or if people disappear.”