A federal judge on Monday refused to block a law that requires Arizona voters to present identification before casting a ballot. A number of challengers had sued to prohibit election officials from enforcing the registration and polling place identification requirements. Critics said that the law would disenfranchise voters, particularly minorities and the elderly, and that requiring voters to acquire and produce identification would be burdensome in time, money and effort. US District Judge Roslyn Silver's order came a day before Tuesday's primary, the first statewide election for which voters will be required to show identification. The law has already been used in some municipal elections.