A federal judge Thursday declared a Florida election law harsh and impractical for requiring groups conducting voter registration drives to turn in registration forms within 48 hours of collecting them, and blocked enforcement of the deadline.

Hours later, the U.S. Justice Department sent a letter to Florida Secretary of State Ken Detzner Thursday evening demanding the state cease purging its voting rolls because the process it is using has not been cleared under the Voting Rights Act, Talkingpointsmemo.com reported.

The DOJ also said Florida's voter roll purge violated the National Voter Registration Act, which stipulates that voter roll maintenance should have ceased 90 days before an election, which given Florida's Aug. 14 primary, meant May 16.

Five of Florida's counties are subject to the Voting Rights Act, but the state never sought permission from either the Justice Department or a federal court to implement its voter roll maintenance program. Florida officials said they were trying to remove non-citizens from the rolls, but a flawed process led to several U.S. citizens being asked to prove their status or be kicked off the rolls.

The nonpartisan League of Women Voters and other groups had challenged the law, passed by Florida's Republican-controlled legislature last year and signed by Republican Gov. Rick Scott with the stated intent of fighting voter fraud.

Critics have said the law's effect would be to suppress registration of voters who would be likely to vote Democratic, Reuters reported.

The law imposed a $1,000-a-day fine on groups that fail to give election authorities voter registration forms filled out by Floridians within the 48-hour deadline. The League of Women Voters said the requirement was so onerous that it stopped holding voter registration drives in Florida after doing them for 72 years.

Ruling in the state capital of Tallahassee, U.S. District Judge Robert Hinkle granted a preliminary injunction also blocking enforcement of other parts of the law putting new restrictions on groups conducting voter registration drives.

The judge also blocked a requirement that voter registration groups notify the state within 10 days if any volunteer or employee stops working for the organization.

Hinkle said the law and state regulations implementing it impose burdensome record-keeping and reporting requirements that serve little if any purpose, thus rendering them unconstitutional.

Under federal law, organizations have the right to collect and mail in voter registration forms, but the harsh and impractical 48-hour deadline effectively prohibited them from using the mail, the judge said in his ruling.

When a plaintiff loses an opportunity to register a voter, the opportunity is gone forever, Hinkle wrote. And allowing responsible organizations to conduct voter-registration drives —thus making it easier for citizens to register and vote - promotes democracy.

Florida Department of State spokesman Chris Cate told the Associated Press the agency, which runs elections, was looking at its options, which could include an appeal or resolving the judge's concerns through administrative rules. Cate said the portions of the law Hinkle left standing are more important than those he blocked. 

President Barack Obama's re-election campaign praised Hinkle's ruling. Voting should be easy and accessible, and we're working to get as many Americans involved as possible, said Eric Jotkoff, a Florida Obama campaign spokesman. Florida is a key battleground state in the presidential election.

The League of Women Voters and other voting rights groups that joined it in the lawsuit said the state's previous election law, which required groups conducting voter-registration drive to promptly deliver registration forms, was working well. The judge said the state had produced no evidence to the contrary.

The groups argued that other parts of the law violated citizens' constitutional rights to vote and to speak freely. The judge said they were likely to prevail at trial on the merits of their challenge.

Other groups challenging the registration provisions are the Rock the Vote group that focuses on young people and the Florida Public Interest Research Group Education Foundation.

The case pending in Washington is a court review of the three election law sections to determine if they comply with the federal Voting Rights Act. The Justice Department as well as several interveners, including the League of Women Voters, contend they violate the law by suppressing minority voting.

We are hopeful that this ruling will enable us to continue this important work. Florida's anti-voter law creates impassable roadblocks for our volunteers, who are simply trying to bring fellow citizens into our democratic process, said Deirdre MacNab, president of the League of Women Voters of Florida.

The Florida law was part of a wave of what critics called voter suppression laws backed by Republicans and enacted in 15 states last year.

The Brennan Center for Justice at New York University School of Law represented the plaintiffs in the Florida case. It said the laws could make it harder for millions of eligible Americans from voting in the November election and that minorities, poor people, the elderly and young voters would likely be most affected.

Florida Republican Party Chairman Lenny Curry said the 48-hour rule would have ensured that voter registration groups were held accountable and that citizens were registered in a timely and proper manner.

Scott said he was pleased that the judge let stand some of the law's provisions. Our democracy relies on ensuring only valid, legal votes are counted, and that starts with having a voter registration process that safeguards the ballots of Florida citizens, the governor said.