Easy to get, hard to trace
Back in the US, where the Second Amendment upholds the gun shows that some consider a loop hole that facilitates weapons smuggling, the politics surrounding tracing and information sharing can be complicated, while the process of purchasing and required background checks has been streamlined.
Background checks are not always required at gun shows because most sales are considered to be made between two private, unlicensed individuals - not a licensed dealer and an individual, as would be the case in gun stores where a background check is mandatory.
The check itself is often quick and easy. When a customer is ready to close a sale, the merchant is required to call a hotline administered by the Federal Bureau of Investigations, where he gives the appropriate information to the person on the other end of the line. Most of the time this process takes less than five minutes. For years, the process took much longer, to the chagrin of gun shop owners, but over time has become streamlined and easy, according to Litzman.
Strawmen who purchase weapons from law abiding gun merchants are a gateway into the murky world of the grey market, where the guns reside until they are smuggled into Mexico and resold. Before the guns are handed out for criminal use, expert gunsmiths inspect working parts, clean the guns and make the necessary adjustments to turn a semi-automatic into a fully automatic assault weapon.
Once the strawman leaves the store with gun in hand, or leaves the fairgrounds in the case of a gun show, there is no way to trace the weapon until it is found at a crime scene or seized. Often times, weapons seized in Mexico trace back to gun stores in the US, but the only information the gun dealer must legally share is the information already approved by the background check itself. From there it is a dead end.
Tracing weapons captured in Mexico back to the US is itself a complicated process, one only allowed through the federal police headquarters in Mexico City. As a result, many weapons remain untraced because agents do not want to hassle with the bureaucracy.
There are over 200 million guns owned in the US. At any time any of these guns could be sold to men and women who will smuggle them to Mexico - some for personal use and self-defense and others for criminal use. The combination of such a massive supply with demand met by ant-trafficking creates a sea of possibilities, variables and actors in a country where the ATF and others have a limited set of legal tools and, more importantly, constitutional rights to respect and defend.
Guns: The bloody US-Mexico market / ISN