Mexicans have a right to own firearms, but legal purchase from the only two Mexican gun shops in Mexico City and Monterrey, controlled by the Army, is extremely difficult. In other cases the guns are obtained through Guatemalan borders, "Mexican Cartels Get Heavy Weapons from Central America, U.S. Cables Say", Latin American Herald Tribune, La Jornada, and Wikileaks. or stolen from the police or military, or bought from corrupt officials. Consequently, black market firearms are widely available. Many firearms are acquired in the U.S. by women with no criminal history, who transfer their purchases to smugglers through relatives, boyfriends, and acquaintances who then smuggle them to Mexico a few at a time. The most common smuggled firearms include AR-15 and AK-47 type rifles, and FN 5.7 caliber semi-automatic pistols. Many firearms are purchased in the United States in a semi-automatic configuration before being converted to fire as select fire machine guns. In 2009, a combined total of more than 4,400 firearms of the AK-47 and AR-15 type, and 30% of AK-47 type semi-automatic rifles seized in Mexico have been modified as select fire weapons.

There are multiple reports of grenade launchers being used against security forces, and at least twelve M4 Carbines with M203 grenade launchers have been confiscated. It was believed that some of these high powered weapons and related accessories may have been stolen from U.S. military bases. However, while many U.S. military grade weapons such as grenades and light anti-tank rockets are acquired by the cartels through the huge supply of arms left over from the wars in Central America and Asia, a report from the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) found combination weapons that were counterfeits whose specific courses could not be identified. It has been reported that there have been 150,000 desertions from the Mexican army during 2003 to 2009. Stated another way, about one-eighth of the Mexican army deserts annually.Hector Tobar, "A cartel army's war within", Los Angeles Times, May 20, 2007. Many of these deserters take their government-issued automatic rifles with them while leaving. Some of those weapons originate from the United States. It has been determined that at least some of the M203 grenade launchers and M16A2 assault rifles cited above are of counterfeit origin manufactured for the cartels, possibly to resemble the weapons carried by the Mexican Special Forces.

Gun origins

The U.S. government, primarily through ATF, ICE and Customs and Border Protection, is assisting Mexico with technology, equipment and training. Project Gunrunner is part of the ATF's effort to collaborate with the Mexican authorities and its "cornerstone" has been the expansion of eTrace, a computerized system to facilitate tracing guns which were manufactured in or imported legally to the United States.

"According to [U.S.] Justice Department figures, 94,000 weapons were recovered from Mexican drug cartels in the five years between 2006 and 2011, of which 64,000 -- 70 percent, according to Jim Moran -- come from the United States." The percentages pertaining to the origin of weapons confiscated from organized crime and drug cartels may not be accurately reported. Said numbers represent only firearms Mexican authorities asked the US to trace (7,200 firearms) and that the ATF was able to trace (4,000 on file, of which 3,480 from US). US ATF Mexico City Office informed Mexican authorities ATF had eTrace data only on firearms made in or imported into the US and told them not to submit firearms that lacked US maker or US importer marks as required by US law. The guns submitted for tracing were only firearms that appeared to be US origin. The remaining guns were not submitted for tracing, or were not able to be traced. "In fact, the 3,480 guns positively traced to the United States equals less than 12 percent of the total arms seized in Mexico in 2008 and less than 48 percent of all those submitted by the Mexican government to the ATF for tracing. This means that almost 90 percent of the guns seized in Mexico in 2008 were not traced back to the United States."

Since 1992 (and as recently as 2009), the Congressional Research Service has stated that the ATF tracing system (eTrace) was not designed to collect statistics. Nevertheless, in February 2008, William Hoover, Assistant Director for Field Operations of ATF, testified before Congress that over 90% of the firearms that have either been recovered in, or interdicted in transport to Mexico originated from various sources within the United States.Hoover, William (February 7). "STATEMENT AT THE UNITED STATES HOUSE OF REPRESENTATIVES COMMITTEE ON FOREIGN AFFAIRS SUBCOMMITTEE ON THE WESTERN HEMISPHERE". ‘’Statement by William Hoover, Assistant Director for Field Operations, Bureau of ATF’’. Washington, D.C.: UNITED STATES HOUSE OF REPRESENTATIVES - COMMITTEE ON FOREIGN AFFAIRS. . Retrieved 2009-03-21. However, following a review by the U.S. Office of the Inspector General (OIG) in September 2010, the ATF admitted that “the 90% figure cited to Congress could be misleading because it applied only to the small portion of Mexican crime guns that are traced.” During this 2010 review by the OIG, the ATF could not provide updated information on the percentage of traced Mexican crime guns that were sourced to (that is, found to be manufactured in or imported through) the United States. The November 2010 OIG analysis of ATF data suggest a low percentage of successful weapons traces, ranging from 27% to 44%. In February 2011, Stratfor Global Intelligence calculated the number to be situated between 12% and 48%, and reported almost 90 percent of the guns seized in Mexico in 2008 were not traced back to the United States. The OIG analysis of ATF data concluded that ATF's attempts to expand gun tracing in Mexico have been unsuccessful. While the United States is not the only source of firearms and munitions used by the cartels, ATF says that it has been established that a 'significant' percentage of their firearms originate from gun stores and other sources in the U.S. ATF also says it is well-established that firearms traffickers often use the same routes as drug traffickers. Increasingly, ATF finds that Mexican cartels transport firearms and munitions into Mexico from Guatemala, situated on Mexico's southern border.

Although the number of trace requests from Mexico has increased since February 2006, most guns seized in Mexico are not traced. Moreover, most trace requests from Mexico do not succeed in identifying the gun dealer who originally sold the gun, and the rate of successful traces has declined since the start of Project Gunrunner. Most Mexican crime gun trace requests that were successful were untimely and of limited use for generating investigative leads. Senior Mexican law enforcement authorities interviewed by U.S. OIG officers do not view gun tracing as an important investigative tool because of limitations in the information tracing typically provides and because ATF has not adequately communicated the value of gun tracing to Mexican officials.

If ATF or Mexican police does not collect tracing information quickly, it becomes unavailable. In accordance with Mexican law, all guns seized by the Mexican government must be surrendered to the Mexican Army within 48 hours. It was determined that after the Mexican military obtains custody of the guns, ATF or Mexican federal police are unlikely to gain timely access to them to gather the information needed to initiate traces. Mexican Army officials interviewed by OIG personnel said their role is to safeguard the weapons and that they have no specific authority to assist in trafficking investigations. To gain access to the weapons, ATF officials must make a formal request to the Attorney General of Mexico for each gun, citing a specific reason that access is needed, demonstrating that the requested information is related to a Mexican criminal investigation, and providing a description of the gun with the serial number. Yet, if ATF had the gun description and serial number, ATF officials would not need to request access to the gun. Due to these barriers, ATF and wider Department efforts to gain access to weapons in Mexican military custody have not been successful. Because many weapons are transferred to the military before basic information is collected, and many weapons for which information is available are not traced, the majority of seized Mexican crime guns are not traced. The report states that the poor quality of the tracing data and the resulting high rate of unsuccessful traces suggest that the training is insufficient, training has been provided to the wrong people or there are other unidentified problems with Mexican law enforcement's crime gun tracing.

The final OIG report, which was released in November 2010, concludes that because ATF has not been able to communicate the value of gun tracing to Mexican law enforcement officials, they are less likely to prioritize their efforts to obtain tracing information from seized crime guns and enter it into eTrace. This hinders ATF's plans to deploy Spanish eTrace throughout Mexico. Because the expansion of tracing in Mexico is the cornerstone of Project Gunrunner, this presents a significant barrier to the successful implementation of ATF's Gunrunner strategy. The OIG report also revealed ATF has been unable to respond to many training and support requests from Mexican government agencies, and ATF's backlog of requests for information from Mexican authorities has hindered coordination between ATF and Mexican law enforcement. In addition, it was found that ATF has not staffed or structured its Mexico Country Office to fully implement Project Gunrunner's missions in Mexico.

In 2009, Mexico reported that they held 305,424 confiscated firearms, but submitted data of only 69,808 recovered firearms to the ATF for tracing between 2007 and 2009. Some analysts claim the sample submitted for tracing is preselected to represent the guns that Mexican authorities suspect are US origin.Scott Stewart, "Mexico's Gun Supply and the 90 Percent Myth", STRATFOR Global Intelligence, 10 February 2011. The US Congress has been informed that ATF agents working in Mexico routinely instruct Mexican authorities "to only submit weapons for tracing that have a likelihood of tracing back to the U.S .... instead of simply wasting resources on tracing firearms that will not trigger a U.S. source." This policy skews the pool of weapons submitted for tracing to weapons already suspected of being US origin.Memo to Kenneth Melson, Acting Director ATF, from Sen Charles E. Grassley, Senate Committee on the Judiciary, 16 June 2011. Gun-rights groups use the absolute number between seizures and traces to question whether the majority of illegal guns in Mexico really come from the United States.Study: U.S. lacks strategy to fight arms smuggling into Mexico. CNN News. June 18, 2009. Retrieved 2010-11-07 Gun control advocates use the 48% to 87% successful US origin trace rate to call for re-enactment of the sunsetted Federal Assault Weapons Ban of 1994-2004."U.S. Guns Are Fueling Mexican Drug Violence" Brady Campaign.

A significant source of Mexican cartel weapons is legal sales by U.S. gun companies to the Mexican military and police, sales approved by the U.S. State Department which after they arrive in Mexico end up in cartel hands. In 2011 CBS News reported "The Mexican military recently reported nearly 9,000 police weapons "missing."" A 2009 U.S. State Department audit showed 26 percent of guns sold legally to governments in Mexico and Central America were diverted to the wrong hands.Sharyl Attkisson, "Legal U.S. gun sales to Mexico arming cartels", CBS News, 6 Dec 2011.

Project Gunrunner