MADISON — A Wisconsin law requiring voters to show photo identification at the polls is constitutional, a state appeals court ruled Thursday in a decision offering hope for Republicans working to reinstate the mandate.

The 4th District Court of Appeals ruled the Legislature has the power to make voters identify themselves and the photo identification requirement extends from that authority. The decision reversed Dane County Circuit Judge Richard Niess' finding last year that the law was unconstitutional because it would disenfranchise voters who lack the resources to obtain photo identification.

The ruling doesn't mean the requirements are back in effect; another injunction blocking the law in a separate case still stands and two federal challenges are pending. Republican Gov. Scott Walker's spokesman released a statement calling the ruling a victory, but the general GOP response was measured.

"This is certainly a huge step in the right direction for photo ID laws," Rep. Jeff Stone, R-Greendale, the law's chief author, said in a statement. "However, there are still major hurdles to clear within the court system."

The photo identification requirement has been flashpoint of controversy since Stone and his fellow GOP lawmakers put it in place in June 2011.

The law requires voters to show either a state-issued ID card, valid driver's license, U.S. passport, a student ID that expires within two years or a military ID. The GOP argues the measure will help combat voter fraud. Democrats counter that Republicans have never produced evidence of any widespread fraud in Wisconsin and the mandate would keep poor people, immigrants and senior citizens from voting.

The League of Women Voters filed a lawsuit in October 2011 maintaining the law creates an additional qualification for voters not contained in the Wisconsin Constitution, imposes such a burden on voters it essentially denies them the right to vote and the Legislature exceeded its authority when it passed the mandate. The NAACP's Milwaukee branch and immigrant group Voces de la Frontera filed a lawsuit challenging the law three months later.

Municipal clerks required photo ID at the polls for the first time during the February 2012 primary. Niess issued a permanent injunction in the league's case blocking the requirement a month later. Dane County Circuit Judge David Flanagan followed suit in July, issuing a permanent injunction in the NAACP-Voces de la Frontera case. The state Department of Justice appealed both injunctions. The 2nd District Court of Appeals has yet to rule in the NAACP-Voces de la Frontera appeal.

The 4th District Court of Appeals, though, concluded unanimously the league failed to show how the photo ID requirement violates the constitution.

Judge Brian Blanchard, a former Democratic Dane County district attorney, wrote in the decision the league has conceded the Legislature can require voters to identify themselves. He pointed to an 1856 Wisconsin Supreme Court case that held legislators can require voters to furnish any proof of identity necessary to preserve election integrity. In light of that ruling, requiring photo ID doesn't amount to a new qualification for voters, Blanchard wrote.

The league didn't develop its argument that the requirement imposes expenses and inconvenience on voters, Blanchard added, noting the state Department of Transportation offers free photo ID cards if applicants say they need them to vote.

The league issued a statement saying it regrets the appeals court overturned Niess' "strong ruling." Lester Pines, the organization's attorney, said he plans to discuss with the league whether to ask the state Supreme Court to take the case.

"I don't agree with the court of appeals decision," Pines said. "They overlooked a fundamental problem, which is the law, regardless of how you apply it, ends up disqualifying fully qualified voters from voting."

Republican Attorney General J.B. Van Hollen released a statement praising Thursday's ruling.

"From the start, we have defended the constitutionality of Wisconsin's voter ID law," Van Hollen said. "While today's decision is an important step toward full vindication of the law, we recognize that other challenges are still pending that address different issues. We will continue to defend the law and look forward to favorable decisions in those other cases as well."

Federal challenges from the American Civil Liberties Union and the League of United Latin American Citizens of Wisconsin are pending in Milwaukee. A status conference in both cases has been set for July 29.

Stone, the law's key author, began circulating a new bill last week that would let poor people opt out of showing photo ID in hopes of negating all the legal challenges.

"I am optimistic," Stone said in his statement, "that the Wisconsin State Assembly will take this bill up in the near future so photo ID laws will soon be in place and voters will have confidence in our electoral system."