The Brady Act has also aided police in tracking criminals who use false identities and in fighting crime after the fact. The Justice Department's study includes results from half a dozen states that use the background checks to find suspects on outstanding warrants. Virginia led with 775 arrests last year, a whopping 30 percent of the state's 2,568 rejections. Mr. Ashcroft has vowed that federal prosecutors would reinforce this practice by arresting people who act illegally by trying to buy guns.