CHICAGO - Gov. Rod Blagojevich signed on Friday legislation that requires background checks on potential firearms buyers at gun shows, closing a loophole police and others contend has been exploited by gangs and other illegal buyers. Background checks are already required for people buying guns at licensed stores to ensure they don't have a criminal record that would bar them from possessing firearms. The new law, which applies to unlicensed dealers, has long been sought by gun-control advocates and police. "Today is a step in the right direction," Blagojevich said. "It's a step for sane and commonsense gun laws, gun...