Early voting begins Monday in Texas, and voters will have to show photo identification to cast a ballot.
A federal judge had struck down the voter ID requirement as unconstitutional last week, but on Tuesday, an appeals court temporarily reinstated the law. It was too close to the election to change the rules, the court said.
"The judgment below substantially disturbs the election process of the State of Texas just nine days before early voting begins," the court said. "Thus, the value of preserving the status quo here is much higher than in most other contexts."
The ruling is not the final word in the case, and the appeals court will rule on the merits of the law sometime after the election.
Under the law, which was passed in 2012, voters in Texas must show one of seven approved photo IDs to access the polls. The U.S. Department of Justice has condemned the law as discriminatory to minorities and estimated that 600,000 voters who are mostly black or Latino lack the required ID.
A federal judge agreed with the Justice Department last week, striking down the Texas law and comparing it to a poll tax.
That may or may not be the case, but for now, the appeals court said it would cause too many logistical problems to retrain the state's 25,000 poll workers.
"Inconsistencies between the polling stations seem almost inevitable given the logistical problem of educating all of these polling officials within just one week," the court said. "These inconsistencies will impair the public interest.