The ruling from the 9th U.S. Circuit Court of Appeals on Thursday came a month before the Nov. 7 general election, and just before Monday's deadline to register. The law had already been used for the Sept. 12 primary and in some municipal elections.

The 2004 law requires that voters at polling places produce government-issued picture I.D. or two pieces of other non-photo identification specified by the law. Other parts of the law dealt with ineligibility of illegal immigrants to receive some government services and benefits.

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.