Madison - In approving one of the strongest photo ID requirements in the country for voters, GOP lawmakers and Gov. Scott Walker violated a few little-noted paragraphs of the state constitution - so say opponents of the law who are preparing a legal challenge to it.

But Republicans dismissed that claim, saying that in writing the legislation earlier this year they took care not to violate the federal or state constitution. They said the current objections over the state's charter show photo ID opponents are recognizing the difficulties of a federal lawsuit over the law.

A lawsuit being prepared by the League of Women Voters of Wisconsin will allege that the law violates right to vote provisions of the state constitution not present in the U.S. Constitution. The group plans to file its lawsuit in Dane County Circuit Court, its attorney Lester Pines said.

"It is absolutely clear that the Legislature paid no attention to the (right to vote) provisions of the Wisconsin Constitution when it passed voter ID," Pines said. "I'm not aware of any point in which they came up."

Pines said that requiring a photo ID amounts to another restriction on voting that isn't authorized by the state constitution. He said that small numbers of state residents are citizens but lack a birth certificate because of unusual circumstances in their lives, making it difficult to obtain an ID.

The law will require voters to show photo identification at the polls starting with next year's presidential primary. The law approved in May ended a decade-long quest by GOP officials and made Wisconsin the 11th state to have approved requiring some form of photo ID at the polls.

Democrats say the $7 million measure is costly and unnecessary and will do little to prevent voter fraud while disenfranchising minority, elderly and rural voters. Republicans say the measure should prevent voter fraud and provide more public confidence in elections.

Rick Esenberg, a Marquette University law professor and the head of what he describes as a "conservative public-interest law firm," said that he believes opponents of the photo ID law are focusing on the state challenge because Republican supporters of the law did a good job of following rules laid out by earlier federal Supreme Court decisions on voter ID laws in other states.

But he doubted the challenge would meet the high burden needed to prove beyond a reasonable doubt that the law was unconstitutional.

"It's an interesting argument, and I can see why (opponents) want to do it rather than beating their head against the federal wall," said Esenberg, who is the president of the Wisconsin Institute for Law & Liberty.

Constitutional question

The federal Constitution does not have right-to-vote provisions, but the state constitution does, laying out that "every United States citizen age 18 or older who is a resident" of Wisconsin may vote in their respective district. The Legislature may restrict that right by passing laws requiring voter registration and proof of residency as well as laws to exclude felons and those judged mentally incompetent, according to the constitution.

The constitution makes no explicit reference to allowing or prohibiting a photo ID requirement.

"If anyone is denied the right to vote, that's a big deal because that's an absolutely fundamental right," Pines said.

Esenberg said he believed that courts would ultimately see the photo ID requirement as an extension of the requirements to prove residency and register to vote that are allowed by the constitution.

"It would allow (officials) to say you are who you say you are," Esenberg said.

Pines countered that the photo ID doesn't have a strong link to proving residency since a driver's license can be used by a registered voter to cast a ballot, even if it has an outdated address that doesn't match a voter's registered address.

Sen. Mary Lazich (R-New Berlin), chairwoman of the Senate Transportation and Elections Committee, said she couldn't remember any testimony on the photo ID bill dealing with the issue being raised by the League of Women Voters.

But she emphasized that Republicans took a number of steps to protect voters, including allowing those who do not show a photo ID to still cast a provisional ballot that would be counted if the voter shows photo ID to an election clerk by the Friday after the election.

Under the new law, voters have to show either Wisconsin driver's licenses, state-issued ID cards, certain very limited student IDs, military IDs, passports, naturalization certificates or IDs issued by a tribe based in Wisconsin. Those living in retirement homes, nursing homes and institutions are exempt from the law, as are victims of stalking and those who opposed having their photos taken for religious reasons.

"I just can't stress enough how far we went to make sure no one was disenfranchised," Lazich said. "They're grabbing at straws."

Janine Geske, a Marquette University Law School professor and a former state Supreme Court justice, said the challenge was "not a frivolous" one, given the very specific language in the state constitution. She said, however, that it would likely not succeed because it faced a high burden of proof and a state Supreme Court that would be unlikely to be receptive.

The challenge could not be appealed beyond the state Supreme Court.

"It's certainly an argument that is worth making," Geske said. "Do I think it's going to be successful? No."

A challenge to the law in federal court could also still happen. For instance the liberal group One Wisconsin Now has said it's considering a lawsuit of its own

Executive director Scot Ross declined to speak about any possible federal lawsuit Friday but said the language of the state constitution showed that its framers saw the right to vote as something "sacred" that could not be restricted lightly.