The Obama administration approved a rule requiring gun dealers in Arizona, New Mexico, California and Texas to inform the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) if a person buys more than one semiautomatic rifle that accepts a detachable magazine and uses ammunition greater than .22 caliber within five days. The rule is an attempt to make it more difficult for Mexican drug cartels to purchase weapons. Straw buyers often purchase guns, which are then smuggled back to Mexico