The American Civil Liberties Union filed a federal suit on Friday against Tennessee's Secretary of State, aimed at protecting grassroots voter registration drives, a release from the nonprofit states.

The suit seeks a preliminary injunction to stop a new Tennessee law from going into effect Oct. 1, in a state with the 49th lowest voter turnout.

It would impose both criminal and civil penalties on organizations that host voter registration drives if they return incomplete applications or fail to comply with certain requirements.

“Civic-minded groups like our clients should be able to help community members register to vote without the threat of being charged with a crime or slapped with an exorbitant fine,” said ACLU-TN Executive Director Hedy Weinberg in a Friday release.

The injunction, if granted, would halt the implementation of the bill, pending the outcome of the suit. This would allow such organizations to "encourage political participation through voter registration efforts," and prevent the active penalties provided for in the bill.

“While this case works its way through the system and we prove in court why this law is unfair and unconstitutional, our clients should be able to help as many Tennesseans as they can gain access to the ballot box," Weinberg said in the release.

Bill imposes fines, penalties for incomplete forms

Under the controversial law, HB 1079/SB 0971, a person or organization conducting a voter registration drive could face civil or criminal penalties if they file 100 or more registration forms that are "deficient" or "incomplete."

Gov. Bill Lee signed the GOP-backed legislation in May.

The bill would likely make Tennessee the first to fine voter registration groups for turning in too many incomplete signup forms, prompting a previous federal lawsuit and protests by critics who said it would suppress efforts to register minorities and other voters.

Tennessee's NAACP chapter and other groups immediately sued the state after Lee signed the bill, which was backed by Republican Secretary of State Tre Hargett and is set to take effect in October. Among other steps, the measure would allow criminal penalties for submitting registration forms too late and for shirking other new regulations.

Hargett, in his role as Secretary of State, is named as the defendant in the new suit. Other election commission officials were also named.

The Lawyers' Committee for Civil Rights Under Law, a nonprofit, helped file the earlier lawsuit, which alleges that the law would "violate the due process clause of the Fourteenth Amendment and have a chilling effect on the exercise of fundamental First Amendment rights." The group called the law "one of the most restrictive voter suppression measures that we have seen this year."

Plaintiffs in the current suit include:

League of Women Voters of Tennessee,

League of Women Voters of Tennessee Education Fund,

American Muslim Advisory Council,

Mid-South Peace & Justice Center,

Rock the Vote,

Spread the Vote,

Memphis Central Labor Council

and HeadCount.

In June, members of HeadCount, another organization that holds voter registration drives, often at festivals like Bonnarroo, said the potential restrictions are "scary."

HeadCount hosts events at more than 1,000 concerts and festivals each year. It has been at Bonnaroo since 2004 — where it consistently sets records for registration, including more than 1,390 new voters this year. About half of those are from Tennessee, said Andy Bernstein, executive director of HeadCount.

But the new state legislation could discourage others from helping encourage voter participation, voter registration organizers say. Tennessee's law would impose civil fines for submitting more than 100 incomplete forms. The Class A misdemeanors would carry fines up to $2,500.

"Our fear is that it becomes too risky to register Tennessee voters," Bernstein said.

Voter turnout limited in Tennessee

Tennessee, meanwhile, is ranked second to last in the nation for voter turnout and nearly as bad in voter registration.

Hargett noted previously that many of the 10,000 registrations submitted in and around Memphis last year by the Tennessee Black Voter Project on the last day for registering were filled out incorrectly. Critics have questioned whether the bill has anything to do with the fact that it signed up about 86,000 people to vote in last year's election.

Hargett rejected the notion in April that the legislation arose out of the increased effort to register African Americans.

"It comes out of a massive number of deficient forms in Shelby and Davidson county," he said.

He said the bill encourages quality voter registration while encouraging online registration.

Reporters Jessica Bliss, Natalie Allison and Joel Ebert contributed to this report. and Reach reporter Mariah Timms at mtimms@tennessean.com or 615-259-8344 and on Twitter @MariahTimms.