Here is an excerpt from this article in the Latin American Herald Tribune:
"The most fearsome weapons wielded by Mexico’s drug cartels enter the country from Central America, not the United States, according to U.S. diplomatic cables disseminated by WikiLeaks and published on Tuesday by La Jornada newspaper. Items such as grenades and rocket-launchers are stolen from Central American armies and smuggled into Mexico via neighboring Guatemala, the U.S. Embassy in Mexico City reported to Washington... The cables’ authors note that Mexican officials and politicians never hesitate to remind U.S. diplomats that Mexico’s drug war – which has claimed 35,000 lives in the last four years – is fueled by Americans’ demand for illegal drugs and by guns bought in Arizona, New Mexico and Texas. Yet one of the cables maintains that 90 percent of the heavy armament Mexican security forces seize from cartel gunmen comes from Central America. The cable, which does not offer any particulars or supporting documentation, does acknowledge that the vast majority of the handguns and many of the assault rifles used by the cartels enter Mexico from the United States." Link to Full Article
Analysis: I won't argue with the claim that the majority of military-grade heavy weaponry used by Mexican DTOs comes from sources other than the US; I actually never have. Unlike pistols and rifles, it's pretty hard for anyone - US citizens included - to get their hands on that stuff, so it would logically follow that DTOs would look to corrupt Mexican police/soldiers or suppliers in Central America and Asia for stuff like grenades and rocket launchers.
I feel like whenever these kinds of articles are published, the writers are trying to say, "See? The US and our gun laws aren't the big problem; the stuff's coming from Central America!" There are a lot of people who make the argument that most of the firearms in general being used by DTOs come from foreign sources, and not just the heavy weaponry. That I would argue with, but it's not my point in this post.
What my point is, is that we have no idea what the proportion is of heavy weaponry versus pistols/rifles being used by DTOs on a regular basis, and therefore can't determine exactly what the significance is of where the heavy weapons come from. Let me restate. Based on my experience, I'm under the impression that the majority of attacks conducted by DTOs against each other and against the Mexican army and police involve the use of firearms that can be - and usually are - obtained in the US. We are seeing an increase in the use of grenades in attacks against police stations and media outlets, but it's usually one grenade here, one grenade there. If you look at the major seizures being made by Mexican authorities, there are usually more pistols, rifles, and ammo in the caches than there are grenades, rocket launchers, or other heavy-duty military-grade weapons.
But this is just an educated guess on my part. Ultimately, I don't think anyone's taken a statistical look at reports to determine how often DTOs are using heavy-duty weapons versus light weapons. If my hunch is right, then it may not matter very much that DTOs are getting the harder-hitting weapons from El Salvador or South Korea if most of the killing is being done with US-origin pistols and rifles. Think about the practical aspect of using those kinds of arms. Tactically speaking, pistols and rifles are more useful for the kinds of engagements DTOs are involved in on a daily basis with either rivals, soldiers, or police. Assassinations and urban conflicts that break out almost always involve hand-held assault weapons. It's rare that you'll hear about narcos using an RPG against the military or police, or the tossing of multiple grenades during a firefight.
Again, it's just a guess, but anyone who tries to argue that it's ALL coming from foreign sources is going to have a hard time proving that point with hard evidence.