The Supreme Court ruled Friday that Arizona may require voters to provide photo IDs when they cast their ballots next month.

The justices cautioned that they were not issuing a ruling on the constitutionality of Arizona's law. "As we have noted, the facts in these cases are hotly contested," the court said in an unsigned five-page order.

The ruling merely allows the Nov. 7 election to proceed with the photo ID law in place. Federal courts still will have to resolve a lawsuit contending that the law will disenfranchise numerous voters, particularly the elderly and minorities.

Courts in Georgia and Missouri have blocked similar laws.

Justice John Paul Stevens, in a brief concurring opinion, said the high court's action makes it more likely that the constitutional issues "will be resolved correctly on the basis of historical facts rather than speculation."

The law requires voters to prove citizenship when registering to vote and to show photo IDs when they go to the polls. The law was meant to make sure illegal immigrants weren't casting ballots.

Opponents of the law contend it discourages some people from voting, including the elderly, poor and disadvantaged who don't always carry IDs.

A federal judge ruled the state could enforce the law. But the 9th U.S. Circuit Court of Appeals later blocked it from taking effect for the Nov. 7 election.

In his bid to allow the state to go forward, Arizona Attorney General Terry Goddard told the justices that "voter registration at the polls is an emerging issue of national importance. States have a compelling interest in curbing fraud and protecting the integrity of elections."