(CNN) When Hurricane Matthew struck the United States this month, the deadly storm forced massive evacuations near the end of voter registration for the upcoming presidential election.
Some Southern states extended their deadlines to accommodate residents who may have been prevented from registering to vote because of the storm. Georgia, where state officials called upon more than half a million residents to evacuate coastal areas, did not extend the voter registration deadline.
The American Civil Liberties Union filed a federal lawsuit late Monday against Georgia officials for failing to extend the state's voter registration period.
"Thousands of Georgians will be prevented from participating in the November election," Kathleen Burch, interim counsel for the ACLU of Georgia, said in a statement. "This is unethical and illegal."
The lawsuit accuses Georgia Gov. Nathan Deal and Secretary of State Brian Kemp of acting in violation of the Constitution, the Voting Rights Act and the National Voter Registration Act.
It also claims the state's refusal to extend the deadline discriminates against African Americans, who tend to vote for Democrats. Both Deal and Kemp are Republicans.
Deal's office declined to comment and referred CNN to Kemp's office.
"These liberal groups need to stop trying to change the rules so late in the game and let county officials move forward with early voting and issuing absentee ballots, both of which are already ongoing," Kemp spokeswoman Candice Broce said in an email.
Brunswick, Georgia resident J'Mari Bethea, 18, had planned to register to vote in Glynn County on October 6.
According to the ACLU's lawsuit, Deal ordered an evacuation six days before the end of the voter registration period. Bethea, one of the roughly 500,000 people affected by the mandatory order, returned home five days later -- on the day of the deadline.
Bethea tried to register, but there was a problem: The power was out, so he couldn't access the Secretary of State's website. Likewise, the US Post Office and local government offices had suspended services in Glynn County, the lawsuit said.
Despite the fact that thousands were in Bethea's position, state officials did not grant an extension following the storm, according to the lawsuit.
Julie Ebenstein, a staff attorney with the ACLU's Voting Rights Project, said Deal's opposition was an "affront to the democratic process and to voter participation in this critical election."
Last week, the Florida Democratic Party and several other groups filed a lawsuit against Florida officials over their refusal to extend the deadline. The legal challenge followed registration extensions in North Carolina and South Carolina after Matthew came through.
Ultimately, a federal judge ordered Florida officials to extend its deadline.
Given those extensions, the ACLU now wants a judge to order Georgia to take similar action.
"The fact that registration activity is particularly high during this period is well-known to state and local election officials," according to the lawsuit. "Nevertheless, without any legitimate justification, the state simply refused to follow examples of neighboring states and extend the voter registration deadline in response to this natural disaster."
Ahead of the 2012 election, more than 77,000 Georgians registered to vote during the final days before the deadline, the ACLU said. Nearly half of those signing up to vote near the deadline were black, the lawsuit said.
"Tens of thousands of voters -- who relied on the state's published October 11, 2016, registration deadline, but then found themselves unable to register during the last few days of the registration period -- likely lost their opportunity to register to vote as a consequence," the lawsuit said.
Kemp's office pointed out that South Carolina moved its deadline for mailed applications only, and they moved it to the same day as Georgia's existing deadline.
"Georgia voters in affected areas actually had more opportunities to register than their counterparts in South Carolina," Broce said.
"We were paying close attention to the situation on the coast with Hurricane Matthew, but changing deadlines so close to the election is a bad idea and makes an orderly election more difficult."
On October 14, three days after the deadline, a federal judge ordered Georgia to extend the voter registration deadline in Chatham County. Chatham, where Savannah is located, is the most populous of the state's six coastal counties.
"[It was] the right thing to do," U.S. District Judge William Moore Jr. said
But Deal's and Kemp's offices have refused to extend the deadline for the other five coastal counties -- Bryan, Camden, Glynn, Liberty and McIntosh -- despite several letters from voter rights groups.
The ACLU's lawsuit asks a judge to give residents of those five counties an additional six days to register.
If the deadline is extended, WickFORCE, a Glynn County voter registration group and a plaintiff in the ACLU lawsuit, would be able to get back precious days of canvassing that it lost during Matthew.
With fallen trees and downed power lines, WickFORCE had to suspend canvassing efforts for four days. The group operates in areas with high percentages of minorities.
"There is a long history of official discrimination in voting in Georgia against African Americans, who also suffer from the effects of discrimination in many other areas of socio-economic life, including disparities in employment, health, education, and access to transportation," the lawsuit said. "These disparities make the costs of voter registration more burdensome for African Americans."