Illicit gun-smuggling from the United States to Mexico has increasingly armed organized criminal groups with firearms, including military grade firearms, in their highly lethal territorial disputes with each other and with government security forces. Mexican authorities have claimed that at least half a million firearms are smuggled into Mexico from the United States each year. The unrelenting pace and volume of this flow has earned it the name the “Iron River.”
In this year’s edition of the Mexico Peace Index, we examine the impact of illicit gun-smuggling from the United States to Mexico, a devastating flow which has been referred to as the “Iron River.” This flow has increasingly armed organized criminal groups with firearms, including military-grade firearms, in their highly lethal territorial disputes with each other and with government security forces. Mexican authorities have claimed that at least half a million firearms are smuggled into Mexico from the United States each year.
While it is possible to legally obtain certain guns in Mexico, the process for ownership is highly regulated. Prospective buyers must undergo background checks and submit a range of documentation, including confirmations of the absence of a criminal record. There is also only one store in the country that legally sells firearms to private citizens, which is located on an army base in Mexico City. To circumvent these restrictions, criminal actors have set up illicit pipelines to traffic guns into Mexico. Gun smugglers are known to enlist US residents or citizens to purchase firearms from gun shops or gun shows, in what is known as a “straw” purchase, and then transfer them to a cartel representative.
Traces performed by the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) on guns recovered at Mexican crime have consistently shown that at least two-thirds are smuggled from the United States. Moreover, about three-quarters of those guns originate in southwest border states, particularly Arizona and Texas, where they are brought into Mexico via trafficking pipelines to Sonora, Chihuahua, Nuevo León, Tamaulipas, and Guanajuato. These pipelines, combined with some of the primary drug trafficking routes through Mexico, are illustrated in the Figure below.
Researchers have traced the beginnings of the rise of US guns in Mexico to the expiration of a US federal assault weapons ban in 2004, before which fewer than 90,000 firearms were estimated to be trafficked across the border each year. A 2013 study determined that there was an immediate uptick in firearms homicides in Mexican municipalities close to the US border following the expiration of the ban, except for municipalities bordering California, which was the only US border state to have a state-level assault weapons ban still in place.
The flow of US guns into Mexico has been associated with a substantial deterioration in peacefulness in the country over the past decade. Since 2015, the Mexico Peace Index has recorded a 71.2 per cent increase in the firearms crime rate, as shown in the figure below. This increase has been primarily driven by a rise in homicides committed with a firearm, which now account for nearly 72 per cent of all homicides in Mexico. In the past ten years, it is estimated that over 200,000 people have been killed with guns in the country
As a result of these dynamics, in 2021, the Mexican government filed a lawsuit in US court against several large US gun manufacturers. The lawsuit argued that such companies were liable for facilitating the influx of weapons across the border, claiming that this movement had been a major contributor in Mexico ranking third in the world in gun-related deaths. In addition to the massive human cost, the lawsuit argued that the firearms-related violence associated with this flood of guns had adversely impacted investment and economic development in Mexico. In August 2024, a US judge dismissed the case against six of the eight companies named in the original lawsuit, citing a lack of proof that they had any involvement in facilitating weapons trafficking to cartels in Mexico. In March 2025, oral arguments in the case were made before the US Supreme Court, which is only expected to hand down its decision in June 2025.
Despite these recent developments and trends indicating a decrease in other unlawful flows across the US-Mexico border, the “iron river” continues to flood Mexico with dangerous weaponry. In the hands of criminal organizations, these firearms perpetuate violence, disrupt communities, and impede development, ultimately making peacefulness more difficult to achieve and sustain.
In the past decade, the illegal cross-border flows of drugs and weapons have had devastating impacts on both Mexico and the United States.
Violent criminal organisations in Mexico are largely fuelled and financed by drug trafficking, with most of the supply destined for the United States...
Identificación y medición de los factores que impulsan la paz
Identifying and measuring the factors that drive peace.
