ACLU of Arkansas legal director Holly Dickson, right, speaks on the steps of the Pulaski County Courthouse Wednesday about a lawsuit challenging the state's voter ID law while the organization's executive director, Rita Sklar, and cooperating attorney Jeff Priebe look on. ( Gavin Lesnick

The American Civil Liberties Union of Arkansas is asking a judge to strike down a state law requiring voters to show photo identification before they can cast a ballot, arguing the new requirements violate the Arkansas constitution.

The ACLU on Wednesday filed a lawsuit in Pulaski County Circuit Court on behalf of four voters seeking to overturn the law, which was approved by the Republican-led Legislature last year. The law took effect this year, and its first statewide test will be the May 20 primary. The plaintiffs include a Pulaski County voter who refused to show ID during a March 11 local special election.

In a news conference announcing the lawsuit, ACLU of Arkansas legal director Holly Dickson said the law impairs voters and puts some without birth certificates or photo identifications in a "catch 22" situation in which they need one of those documents to obtain the other.

"The only purpose [the law] is serving is to place an artificial barrier between these voters and the ballot box," she said. "We think it clearly violates the letter and spirit of the Arkansas constitution."

The voters listed as defendants in the suit include a 34-year-old woman who moved to Arkansas after losing her photo ID and birth certificate in Hurricane Katrina; a 23-year-old woman who the ACLU says has tried without success to get an ID and a birth certificate; and a 78-year-old man who was never issued a birth certificate.

The suit was assigned to Pulaski County Circuit Judge Tim Fox. It's unclear when a hearing will be held, but the ACLU said it hopes to get a preliminary injunction issued quickly with a primary election scheduled next month.

"There's certainly permanent harm that will be done, that can't be undone, if one person is disenfranchised with this election," said ACLU of Arkansas executive director Rita Sklar.

Democratic Gov. Mike Beebe vetoed the voter ID measure last year, saying it would infringe on voters' rights. The Legislature overrode his veto with a simple majority.