When the US accuses Mexico of supplying an endless supply of drugs to its 50 states, Mexico's standard response is that the US arms these same drug dealers with its guns. While this is a valid response, it does not tell the full story. The fact is, the US is just about the most expensive place for the cartels to buy arms.
In drug battles that are becoming increasingly violent, the source of these guns, grenades, and other weapons is becoming more and more relevant.
For example, in late-June, 12 members of the highly-trained Los Zetas cartel were killed in a battle, and another dozen were taken prisoner. Police were injured. The local population was terrorized.
Assault rifles, fragmentation grenades, and other ordinance were found, along with up to 15 bodies burned in a mass grave.
Indeed, the US is a major arms producer, and many of these guns and weapons find their way across the border, both legally and illegally.
And let's face it - the US - Mexico border is not airtight. Where there's an economic incentive, weapons, drugs, and people will continue to make their illegal way back and forth.
But the US isn't Mexico's only source of arms, just like it's not the only market for its drugs. Mind-boggling amounts of automatic weapons, ordinance, and military goods have been introduced to Central and South America since the Cold War began. (Though many from the US, in operations such as Reagan's Iran-Contra scandal).
The borders within Latin America are even less-secure than those with the US. Almost every Central and South American nation has been embroiled in some sort of conflict in recent history (barring neutral Costa Rica). Russian, American, Italian, British, even Swedish weapons are to be found.
In fact the Swedish government is asking Venezuelan officials how in the world Columbian FARC members ended up with their sophisticated rocket launchers.
On 27 July, a representative from Swedish weapon manufacturer Saab said, "It is extremely unfortunate that this has occurred, although this is out of our control. Our client is the Venezuelan army. Saab always acts in accordance with Swedish law and international regulations regarding the sale of defense materials."
This is only the most recent of many examples of how legitimate weapon trading can end up fueling rebels, guerillas, and Mexican drug cartels.