Mexico has some of the toughest gun laws in the world.If permits are even granted, the guns must be registered with the military.However, that has not prevented Mexican drug cartels from buying powerful weapons, and most of them come from the U.S.After months of requests, the 10News I-Team was given an exclusive look at what Mexican authorities are up against in their battle with the cartels.In the center of Tijuana is a heavily guarded Mexican military base. Very few people get inside the gates where security is paramount.Almost daily, members of the Mexican military are faced with their ongoing battle against the drug cartels.The day the I-Team arrived, soldiers were sawing through steel plates in the trailer bed of an 18-wheeler. It was a failed attempt by cartel members to move drugs across the border.On this base it is a weekly routine. Week after week, criminals are arrested trying to transport drugs into the U.S.The military puts them on display, showing off the drugs, cash and their dangerous weapons.The I-Team was granted access inside a heavily guarded armory within the gates of the base. Thousands of weapons are stored there, and military officials told 10News they are linked to cartel arrests.The problem with many of these weapons that are confiscated from the cartels is that they are manufactured in the U.S. by the U.S. government.The Bureau of Alcohol, Tobacco, Firearms and Explosives claimed Mexican cartels received about 95 percent of their weapons from American gun sellers.U.S. gun shops are not allowed to sell the high-powered military weapons, and many question how they end up across the border.Marc Halcon is a forensic firearms consultant and works at the American Shooting Center in San Diego. He said U.S. gun shops are taking the blame for supplying the cartels with weapons, but in reality many of these high-powered weapons come from the U.S. government and are given to the Mexican military to fight the cartels.Halcon was asked to help identify the weapons for 10News, their possible origin and how they would end up in the cartels' hands."What you're seeing here, these are all basically military firearms," Halcon told 10News. "We sent millions of dollars -- we meaning the government -- to the war on drugs to the government of Mexico and to the military. And from there they filter their way out."Halcon continued, "Now you're talking about a military that has over 1,200 soldiers a month go AWOL and leave the military to go to the drug dealers' side. Of course when they go, they take the guns with them."Since 2000, an average of 16,000 soldiers a year has deserted the Mexican military. The concern is what they take with them."Through trying to be good neighbors and fighting the war on crime, our U.S. government just sends crates and crates and truckloads of these down to Mexico," said Halcon.10News provided several serial from various weapons to the ATF and other U.S. agencies in an effort to track the origin of those weapons.So far, 10News' requests have either been denied or there has been no response.