The Supreme Court ruled Monday that states can require voters to produce photo identification without violating their constitutional rights, validating Republican-inspired voter ID laws.

In a splintered 6-3 ruling, the court upheld Indiana's strict photo ID requirement, which Democrats and civil rights groups said would deter poor, older and minority voters from casting ballots. Its backers said it was needed to prevent fraud.

It was the most important voting rights case since the Bush v. Gore dispute that sealed the 2000 election for George W. Bush. But the voter ID ruling lacked the conservative-liberal split that marked the 2000 case.

The law "is amply justified by the valid interest in protecting 'the integrity and reliability of the electoral process,'" Justice John Paul Stevens said in an opinion that was joined by Chief Justice John Roberts and Anthony Kennedy. Stevens was a dissenter in Bush v. Gore in 2000.

Justices Samuel Alito, Antonin Scalia and Clarence Thomas also agreed with the outcome, but wrote separately.

Justices Stephen Breyer, Ruth Bader Ginsburg and David Souter dissented, just as they did in 2000.

'Extremely disappointed'

More than 20 states require some form of identification at the polls. Courts have upheld voter ID laws in Arizona, Georgia and Michigan, but struck down Missouri's. Monday's decision comes a week before Indiana's presidential primary.

The decision also could spur efforts to pass similar laws in other states.

Ken Falk, legal director of the American Civil Liberties Union of Indiana, said he hadn't reviewed the decision, but he was "extremely disappointed" by it. Falk has said voter ID laws inhibit voting, and a person's right to vote "is the most important right." The ACLU brought the case on behalf of Indiana voters.

The case concerned a state law, passed in 2005, that was backed by Republicans as a way to deter voter fraud. Democrats and civil rights groups opposed the law as unconstitutional and called it a thinly veiled effort to discourage elderly, poor and minority voters — those most likely to lack proper ID and who tend to vote for Democrats.

There is little history in Indiana of either in-person voter fraud — of the sort the law was designed to thwart — or voters being inconvenienced by the law's requirements. For the overwhelming majority of voters, an Indiana driver license serves as the identification.

Burden 'eminently reasonable'

"We cannot conclude that the statute imposes 'excessively burdensome requirements' on any class of voters," Stevens said.

Stevens' opinion suggests that the outcome could be different in a state where voters could provide evidence that their rights had been impaired.

But in dissent, Souter said Indiana's voter ID law "threatens to impose nontrivial burdens on the voting rights of tens of thousands of the state's citizens."

Scalia, favoring a broader ruling in defense of voter ID laws, said, "The universally applicable requirements of Indiana's voter-identification law are eminently reasonable. The burden of acquiring, possessing and showing a free photo identification is simply not severe, because it does not 'even represent a significant increase over the usual burdens of voting.'"

Stevens said the partisan divide in Indiana, as well as elsewhere, was noteworthy. But he said that preventing fraud and inspiring voter confidence were legitimate goals of the law, regardless of who backed or opposed it.

Indiana provides IDs free of charge to the poor and allows voters who lack photo ID to cast a provisional ballot and then show up within 10 days at their county courthouse to produce identification or otherwise attest to their identity.

Stevens said these provisions also help reduce the burden on people who lack driver licenses.