(CNN) - Wisconsin became the latest state to have its voter identification law struck down by the courts, with a federal judge in Milwaukee on Tuesday concluding that opponents of the requirement have shown it has a "disproportionate impact" on many voters.
Judge Lynn Adelman in Milwaukee ruled the requirement that voters present one of nine forms of government-approved photo ID was in violation of the landmark Voting Rights Act. He issued an injunction blocking enforcement of the law. A state judge had earlier tossed out the law on similar legal grounds.
Wisconsin officials had argued there was a legitimate government interest to prevent voter fraud and impersonation, by requiring those casting ballots to prove their identity.
However, "Act 23 serves the state's interest in orderly election administration and accurate recordkeeping only to the extent that it serves the state's interest in detecting and preventing voter fraud," concluded Adelman. "Act 23 weakly serves the latter interest."
He added "Perhaps the reason why photo ID requirements have no effect on confidence or trust in the electoral process is that such laws undermine the public's confidence in the electoral process as much as they promote it."
The state's Attorney General J.B. Van Hollen, responded, saying, "I am disappointed with the order and continue to believe Wisconsin’s law is constitutional. We will appeal."
It is unclear whether separate appeals of the state and now federal rulings will be resolved before November's statewide elections.
The decision comes a week after a state judge in Arkansas dismissed that state's voter ID law. Courts in Texas, Pennsylvania, and Missouri, have recently done the same.
Thirty states in the U.S. have some form of voter identification law, including 12 that require a photo ID, like Wisconsin. At least a dozen other states have pending or proposed laws in the legislature.
Various coalitions of private plaintiffs, civil rights groups, and the federal government have filed challenges to laws in some states, and have generally been successful on stopping enforcement, at least temporarily.
The issue has become a key part of the Obama administration's domestic agenda.
"Across the country, Republicans have led efforts to pass laws making it harder, not easier, for people to vote," President Barack Obama said in an April 11 speech before the National Action Network. "I want to be clear–I am not against reasonable attempts to secure the ballot. We understand that there has to be rules in place. But I am against requiring an ID that millions of Americans don't have. That shouldn't suddenly prevent you from exercising your right to vote."
His supporters say such laws discriminate against minorities, given that a large percentage of minority voters do not have state-issued identification cards. Nationwide, the NAACP claims a quarter of African-Americans and 16% of Latinos of voting age lack a current government-issued photo ID.
"This law had robbed many Wisconsin citizens of their right to vote. Today, the court made it clear those discriminatory actions cannot stand," said Karyn Rotker, Wisconsin senior staff attorney for the American Civil Liberties Union.
The U.S. Supreme Court in 2008 allowed Indiana's voter ID law to stand, saying at the time the stated goal of stopping voter fraud was a legitimate exercise of legislative power. And the conservative-majority court last June struck down the key enforcement provision of the Voting Rights Act, making it harder for the federal government to have oversight over voting regulations in states with a past history of discrimination at the polls.
Many conservative lawmakers have said the voter ID requirements have not inhibited the ability of minorities to vote.
"The interesting thing about voting patterns now is in this last election African-Americans voted at a higher percentage than whites in almost every one of the states that were under the special provisions of the federal government," Sen. Rand Paul, R-Kentucky, said last August, in response to the high court's ruling. He said he had no problem with photo ID laws. "So really, I don't think there is objective evidence that we're precluding African-Americans from voting any longer."
The Wisconsin case is Frank v. Walker (11-cv-1128).