The ruling by a federal appeals court panel dealt a blow to efforts by Republicans in several states to enact restrictive voting laws.
Lead plaintiff Fair Fight Action said it will look at additional legal options to restore the voters.
The state wanted people who it suspected had moved — around 175,000 people — to jump through additional hoops at the polls if they wanted to vote.
New emails show the governor's office put in an "urgent" request to identify noncitizen voter records shortly before the 2018 midterm elections.
David Whitley drew widespread criticism after he claimed nearly 100,000 noncitizens were on the voter rolls. It turned out many of those people were eligible to vote.
Brian Kemp, the Republican candidate for governor, is in charge of elections and voter registration in Georgia.