Since Mexican President Felipe Calderon assumed office in 2006, the death toll in the war between the government and cartel forces has skyrocketed to more then 34,000, with 15,000 of those deaths coming in 2010.

Federal authorities have reported that more then 60,000 firearms from the United States have been recovered by the Mexican authorities since Calderon took office. Recently tactics used by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) to investigate the flow of guns south of the border have come under Congressional scrutiny.

A recent report by the Center for Public Integrity on efforts to prevent gun trafficking reveals that beyond recent investigations on tactics employed by the ATF, there are several important questions about law enforcement having the resources and statutes necessary to prevent trafficking. The report identifies several limitations undermining efforts to prevent gun trafficking to Mexico.

The absence of federal gun trafficking laws inhibit law enforcement officials:

Without a targeted federal gun trafficking law, prosecutors are forced to rely on other statutes that agents and prosecutors say are difficult to enforce and riddled with loopholes.

Chief among them: a frequently used law against lying on the ATF's Form 4473 at a gun shop - especially in claiming the buyer is purchasing for himself, rather than someone else. But court decisions have made this “straw buyer” charge difficult to prove and judges often don't take it seriously. [....]

A straw buyer must sign a form at the gun shop declaring that they are buying the guns for themselves. Lying on the form is a crime. But in order to prove the lie, a prosecutor often must prove what the straw buyer was thinking when he or she bought the gun. Unless that straw buyer immediately delivers the weapon to someone prohibited from purchasing a firearm - like a convicted felon--all the buyer has to claim is that the gun was bought for personal use.

A decision by the federal 9th Circuit Court of Appeals, however, sets the standard even higher. Under that court's ruling, a buyer may actually lie on the form, as long as he or she is not aware the purchase is for someone who could not buy the gun on their own. As a result, even prosecuting the lowliest worker bee in a gun-running scheme is a challenge, agents say. All the straw buyers have to say is they didn't know the guns were for the cartel.

Insufficient resources have been dedicated to counter gun trafficking efforts:

And despite launching Project Gunrunner in 2006 to stop gun smuggling into Mexico with money earmarked by Congress, the ATF has only 224 agents assigned to the special effort, according to a Justice Department report. The ATF says those agents are currently managing 4,600 open investigations, along with monitoring illegal sales at 8,500 licensed gun shops along the Southwest border.

There is no requirement to report multiple sales of cartel favored long rifles such as AK-47s or AR-15s:

Current laws also keep the ATF in the dark on sales of assault rifles, the cartels' weapon of choice. Recent efforts to require that border gun stores immediately report multiple sales of these rifles to ATF - which might create investigative leads - have so far gone nowhere.

Rarely can guns intended for cartels be intercepted immediately:

The cartels recruit straw buyers with no criminal records, they say, and instruct them to take the guns home until it's clear that the ATF does not have them under surveillance. So in virtually all cartel-related investigations, the ATF has no choice but to let the guns out of the store.

Contacted for comment on the CPI report, former prosecutor and vice president of the Association of Prosecuting Attorneys Steven Jansen said:

Through straw purchasers the Mexican drug cartels continue to arm themselves with military-style weapons such as the AK-47 style assault rifles. This is an urgent concern for U.S. law enforcement as we attempt to stop the flow of drugs into our country and create safer communities along our southern border states. Last November, the U.S. Justice Department's Inspector General Report identified that the Bureau of Alcohol, Tobacco, Firearms and Explosives was handcuffed by ineffective and weak laws, especially for straw buyers.