Politics also bedevil the attempt to classify guns seized during Mexican military and justice operations, and compromise methods used to ascertain Mexico's gun market. In the United States, the right refuses to accept the Department of Justice and Department of State's calculation that ninety percent of guns in Mexico come from US sources, calling it a "myth". Senator Charles Grassley has also alleged that the DOJ's Alcohol, Tobacco, and Firearms division was involved in smuggling arms from the United States, arms which may have killed a Border Patrol Agent in December 2010. New Wikileaks' cables employed by the left suggest the fruitfulness of investigating questions about how US military materiel has made it to Mexico.
Some analysts have pointed out that that the US and its decommissioned military armaments are not the largest part of Mexico's secretive gun market. Firepower is finding its way from China, and in a number of cases old arms arrive from Central and South America. These analysts suggest that the DOJ and State ignore these sources as a way to criticize the sources by which guns arrive in Mexico from the United States. In one investigation, one Houston-area gun shop has had 115 guns sold through its store, all of which ended up being used in crimes in Mexico.
But the US cases are some of the best documented, notwithstanding a 2003 US law that shields the identities of gun dealers whose guns are used in crimes in Mexico. In December 2010 the Washington Post wrote a lengthy article which featured Houston, TX as it is the gun-buying capital for Mexico. Houston is preferred, one long-time ATF agent told the Washington Post reporters, because "you can go to a different gun store for a month and never hit the same gun store." About four or five years ago, ATF initiated Project Gunrunner to interdict and document gun sources. Many of the statistics used in this State briefing document about Gunrunner have been questioned by the right.
Another things is certain: drug traffickers use these arms to defend and protect their hold over an illegal drug market, defending it from rival traffickers or Mexico's authorities. The other thing that is certain is that guns and drugs are intimately linked in the mindset of US law enforcement: the Southwest Border Initiative focuses on shipment of guns and traffic of drugs.