MADISON, Wis. -

A federal court says Wisconsin's voter ID law is unconstitutional.

In a 90-page decision, U.S. District Court Judge Lynn Adelman said the state's voter ID law violates both the federal Constitution and the Voting Rights Act.

Adelman said evidence presented in hearings showed some 300,000 people in Wisconsin lack an ID.

"There is no way to determine exactly how many people Act 23 will prevent or deter from voting," Adelman said in the decision. "But no matter how imprecise my estimate may be, it is absolutely clear that Act 23 will prevent more legitimate votes from being cast than fraudulent votes."

Adelman, a former Democratic state senator appointed to the bench by President Bill Clinton in 1997, said the law also discriminates against minorities in poverty, making it harder for them to vote.

"This is not a political process that is equally open to participation by blacks and Latinos," Adelman said. "It is one in which a disproportionate share of the black and Latino populations must shoulder an additional burden in order to exercise the right to vote."

Republican lawmakers passed the voter ID law and Gov. Scott Walker signed it in 2011. It was only in effect for one primary election in 2012, before it was blocked by state and federal judges.

"He pretty much played legislator today because in the ruling that he put out he said he doesn't see a need for photo ID, doesn't see circumstances that we would ever allow it to move forward, so I think that's really disappointing," Assembly Speaker Robin Vos, R-Burlington, said.

Republican leadership had said they supported Walker's efforts to call a special session to pass a new version of voter ID if courts would strike down the law. But Vos said he was still consulting with the Department of Justice about the ruling, as the judge made statements saying even amendments to the law may not make it constitutional.

"Given the evidence presented at trial showing that Blacks and Latinos are more likely than whites to lack an ID, it is difficult to see how an amendment to the photo ID requirement could remove its disproportionate racial impact and discriminatory result," Adelman said.

"I'm going to do whatever it takes to ensure that we have voter ID in place as quickly as possible," Vos said. "If that means having a special session so we have it in place by the fall then I'm definitely open to doing that, and I support it. If it means that because of Judge Adelman's actions that won't actually occur then we will do whatever we can in the most expeditious manner to make it work."

Assembly Minority Leader Peter Barca, D-Kenosha, called the decision "very strong' and said he hoped that the Assembly wouldn't come back for new legislation, or appeal the decision.

"It seems like they have so low regard for taxpayer money when it comes to spending money in courts to protect their own electoral interests I would hope they would pause, step back and analyze this decision and determine whether or not they really have a case," Barca said.

Walker said in a statement he released Tuesday he believed the law was constitutional and that he was reviewing the decision for potential action.

The attorney general said the same, but that he would appeal the decision to the 7th Circuit Court of Appeals.

The State Supreme Court still must rule on the law after hearing arguments on two cases. But attorney Lester Pines, who is challenging the law on behalf of the League of Women Voters, said even if they upheld the measure, the federal law would supersede it.