A Pennsylvania judge struck down the state's controversial voter identification law on Friday, ruling it is unconstitutional and would disenfranchise voters.
The law requiring Pennsylvania residents to present photo identification has been the subject of heated debate since it was passed in March 2012 by a Republican-led legislature.
It has never been implemented, due to a series of court rulings.
In the ruling issuing a permanent injunction on Friday, Commonwealth Court Judge Bernard McGinley said the law "does not pass constitutional muster."
"Inescapably, the Voter ID Law infringes upon qualified electors' right to vote," he wrote. "Disenfranchising voters through no fault of the voter himself is plainly unconstitutional."
Supporters have said the law is aimed at ensuring that only those legally eligible to vote cast ballots. Critics have said it is designed to keep minority voters, who typically vote Democratic, away from the polls.
The chairman of the state Republican Party, Rob Gleason, said in a statement that he was "extremely disappointed."
"The overwhelming majority of Pennsylvanians support a way to protect their right to vote and combat voter fraud," he said.
The state of Pennsylvania has acknowledged there has never been a case of in-person voter fraud, according to court testimony.
Voter ID laws - which require government-issued identification before voting - have become a political and racial flashpoint across the United States. Democrats generally oppose the measures and many Republicans back them.
About three dozen states have passed laws requiring voters to show ID at the polls. The legality of such measures has been challenged in Wisconsin, Texas and other states.
An attorney for the office of Pennsylvania Governor Tom Corbett issued a statement saying the state was evaluating the ruling and would determine what further legal moves might be appropriate.
The ruling could be appealed to the state Supreme Court, according to the ACLU of Pennsylvania.
The law required voters to show a state driver's license, government employee ID or a state non-driver ID card.
"All the evidence in the case pointed to hundreds of thousands of registered Pennsylvania voters who do not have IDs," said Jennifer Clarke, executive director of the Public Interest Law Center of Philadelphia. "The state is simply unable to get ID into the hands of all the people who needed it."
(Reporting and writing by Ellen Wulfhorst; editing by Gunna Dickson)