The justices overruled a federal appeals court that had ordered Ohio's top elections official to do more to help counties verify voter eligibility.
Secretary of State Jennifer Brunner, a Democrat, faced a deadline of Friday to set up a system to provide local officials with names of newly registered voters whose driver's license numbers or Social Security numbers on voter registration forms don't match records in other government databases.
Ohio Republicans contended the information for counties would help prevent fraud. Brunner said the GOP is trying to disenfranchise voters.
In a brief unsigned opinion, the justices said they were not commenting on whether Ohio is complying with a provision of the Help America Vote Act of 2002 that lays out requirements for verifying voter eligibility.
Instead, they said they were granting Brunner's request because it appears that the law does not allow private entities, like the Ohio GOP, to file suit to enforce the provision of the law at issue.
"It's technical but it amounts to a loss for the GOP and a victory for Brunner," said CBS News legal analyst Andrew Cohen.
About 200,000 of 666,000 voters who have registered in Ohio since Jan. 1 have records that don't match. Brunner has said the discrepancies most likely stem from innocent clerical errors rather than fraud but has set up a verification plan.
McCain campaign manager Rick Davis said lower court rulings have clearly said the HAVA regulations require the secretary of state to match against the list, find where there's been fraud and inconsistencies and report them to counties.
"Why in the world would that not happen? We have the technology, the budget, the means and the manpower to make that happen. Do we really want to have to find out after the fact that we had counties that would have been decided one way or another because the secretary of state didn't bother doing the job the HAVA required?" Davis told reporters on a conference call. "I think the secretary of state ought to do her job," he added.