U.S. judge backs multiple rifle sales reporting WASHINGTON (Reuters) - A U.S. judge on Friday refused to block new federal rules requiring gun dealers in four states bordering Mexico to report the sales of multiple semi-automatic rifles, a victory for the Obama administration. The administration issued the reporting requirements last year despite opposition from the gun industry as part of a stepped-up effort to clamp down on the weapons flowing across the border to violent drug cartels in Mexico. The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) ordered more than 8,000 gun dealers in Texas, Arizona, New Mexico and California to report the sale within five business days of two or more semiautomatic rifles to the same person. That also includes rifles with a caliber greater than .22 and with the ability to accept a detachable magazine. Mexican officials have complained bitterly about guns illegally coming from the United States. Tens of thousands of Mexicans have died in the drug wars since 2006 when the government there decided to take on the cartels. Judge Rosemary Collyer, appointed to the bench by Republican President George W. Bush, found that the ATF's requirement was sufficiently narrowly tailored and that it was rational by focusing on the states that border Mexico. "Congress has effected a delicate balance between ATF's regulation of firearms and the right to privacy held by lawful firearms owners," Collyer wrote in a 21-page ruling. The ATF's reporting requirement "did not disturb that balance." Gun dealers backed by the National Rifle Association, a powerful lobbying organization, and the National Shooting Sports Foundation challenged the requirements arguing that it would effectively require national registration of firearms sales, which they said the ATF was not authorized to do. The gun industry has also said that the rules will have no impact on the cartels but rather burden law-abiding retailers and that the reporting requirement was overly burdensome. "If President (Barack) Obama gets a second term, I think law-abiding gun owners are going to see a lot more of it," Wayne LaPierre, executive vice president of the NRA, told Reuters. These drug cartels ... rape, they rob, they murder they throw people into lions' pits, they're not going to be deterred by a form. That must be some form," he said. The groups plan to appeal the ruling. Some 36,000 reports of multiple handgun sales were made from the four border states in fiscal 2010, according to the ATF. The decision came as the ATF has been under scrutiny in recent months after a sting operation to track guns being smuggled to Mexican cartels went awry.