After Mexican authorities killed one of the country’s most wanted drug lords, ‘El Mencho’ (Nemesio Oseguera Cervantes), Defence Minister Ricardo Trevilla Trejo said about 80 percent of weapons seized from criminal groups originate in the United States. Mexican forces, with US intelligence assistance, located El Mencho at a property in Tapalpa; he led the Jalisco New Generation Cartel (CJNG), a group noted for military-style armaments and rapid territorial growth. His death on February 22 prompted coordinated reprisals by cartel members across multiple states, including attacks on highways, police stations and rival factions.
Cartels and their arsenal
Mexico’s largest cartels — including the Gulf Cartel, the Sinaloa Cartel and the CJNG — possess substantial firepower: military-pattern rifles, high-capacity magazines and, in some instances, explosives and heavy-calibre ammunition. The CJNG is particularly notorious; its forces have used sophisticated tactics and weapons, and the group was implicated in shooting down Mexican military helicopters in 2015. Several cartel leaders carry multi-million-dollar rewards; examples include Ismael Zambada Sicairos (‘El Mayito Flaco’), Ivan Archivaldo Guzman Salazar (‘El Chapito’), Fausto Isidro Meza Flores (‘El Chapo Isidro’) and Juan Reyes Mejia-Gonzalez (‘R-1’ or ‘Kiki’), who is the subject of a $15 million US reward.
Mexico’s firearms rules
Mexican law tightly restricts civilian firearm ownership. The Federal Law on Firearms and Explosives limits legal purchases to small handguns, certain .22 rifles and specified shotguns, and sales are conducted through two military-run stores: DCAM in Mexico City and OTCA in Apodaca, Nuevo León. Buyers face multiple approvals and background checks; military-grade rifles are reserved for the armed forces. Despite these controls, experts say cartels acquire most weapons illicitly, with estimates of southbound trafficking from the US ranging roughly from 200,000 to 500,000 firearms per year.
How weapons reach cartels
Trafficking routes and methods are diverse. Straw purchasers—individuals who buy guns legally for third parties—feed commercial demand into illegal channels, a practice prohibited under the US Gun Control Act of 1968. Weapons also move through unlicensed resellers, theft, corrupt officials inside security forces, and specialized brokers who aggregate and ship arms and ammunition from US commercial sources. Smuggling is often done in small, concealed consignments, sometimes with weapons disassembled. Mexico’s Defence Ministry has reported seizures of large quantities of high-calibre ammunition, including 137,000 rounds of .50-calibre since 2012, about half of which were traced to the Lake City Army Ammunition Plant in Missouri.
Legal and enforcement responses
US federal law bars exporting firearms to non-US residents without ATF authorization; Mexico likewise prohibits unauthorized imports. In 2021, Mexico filed a roughly $10 billion lawsuit in US federal court against major US gun manufacturers (including Smith & Wesson, Beretta USA, Colt and Glock), arguing that industry practices facilitate illegal flows into Mexico. The US Supreme Court later held on June 5 that the Protection of Lawful Commerce in Arms Act (2005) shields manufacturers from such claims where plaintiffs cannot show they ‘aided and abetted’ illegal sales. Mexico has also brought civil suits against specific US gun shops accused of enabling straw purchases; some of those cases remain pending.
US programs and controversies
US enforcement has targeted trafficking networks. From 2018 to 2021 the ATF ran Project Thor to investigate gun trafficking, prosecuting numerous cases, but the programme was defunded in 2022. A more notorious precedent is Operation Fast and Furious (2009–2011), in which agents allowed over 2,000 firearms to be purchased and trafficked to trace buyers to cartel figures; many guns were lost and later used in violent crimes, including the 2010 killing of US Border Patrol agent Brian Terry. Fast and Furious drew severe criticism from Mexican officials and US lawmakers for its operational failures and sovereignty concerns. There have also been accusations—denied by US authorities—that certain counterdrug tactics historically involved manipulating rival criminal groups against each other; scholars generally treat such allegations with caution.
Was the US deliberately arming cartels?
Most scholars and analysts see deliberate, strategic US arming of Mexican cartels as unlikely. Researchers such as Benjamin Smith (University of Warwick) note it is conceivable that US authorities sometimes tolerated or overlooked particular trafficking to pursue intelligence on specific targets, but there is no documented policy to arm groups like the CJNG. Incidents like Fast and Furious are typically presented as operational errors or misjudgments rather than intentional support. Annette Idler (University of Oxford) and others highlight that access to US military-grade ammunition is better explained by market diversion, regulatory gaps and porous supply chains than by a purposeful US initiative to equip criminal organisations.
What would reduce southbound trafficking?
Experts say stemming the flow requires policy shifts and sustained commitment on both sides of the border. Measures include treating firearms exported to Mexico with similar priority and resources as drug and human-smuggling investigations; tightening oversight of gun sales and brokering; improving traceability and data-sharing; and increasing joint investigations and accountability for straw purchasing. Long-term progress depends on coordinated cross-border enforcement, persistent oversight, and political will to align law enforcement priorities and close regulatory gaps that allow diversion of weapons and ammunition to criminal networks.