(Updates with background on the law and statement from governor)
By Brendan O'Brien
MILWAUKEE, July 31 (Reuters) - The Wisconsin Supreme Court on Thursday upheld a state law requiring voters to have photo identification to cast a ballot, although the law remains blocked by an earlier ruling by a federal judge that it is unconstitutional.
The court wrote in its decision that providing a photo identification at the ballot box does not create a substantial burden to the voter, as claimed by the plaintiffs in the case.
"Photo identification is a condition of our times where more and more personal interactions are being modernized to require proof of identity," the court wrote.
Similar voter identification laws have become a political and racial flashpoint across the United States with Democrats generally opposed and many Republicans backing them.
Republicans argue tighter rules are needed to prevent voter fraud. Democrats say voter fraud is rare and that the rules are instead intended to deter poor people, ethnic minorities and college students from voting - groups that are seen as less likely to have identification and more likely to vote Democrat.
"People need to have confidence in our electoral process and to know their vote has been properly counted," Wisconsin Governor Scott Walker, a Republican, said in a statement.
The Wisconsin Supreme Court's decision came in two cases brought by the Milwaukee branch of the National Association for the Advancement of Colored People and the League of Women Voters of Wisconsin Education Network.
The 2012 law has not been in effect because a federal judge ruled the measure unconstitutional in April. Judge Lynn Adelman of the United States District Court for Wisconsin's eastern district said the law clashed with the equal protection clause of the U.S. Constitution.
Wisconsin Attorney General J.B. Van Hollen is appealing Adelman's ruling.
Wisconsin is one of several states that have been forced to defend changes to voting protocol. Judges in recent months have overturned photo identification laws in Pennsylvania and Arkansas. (Editing by Jonathan Allen and Bill Trott)
Wisconsin Supreme Court Upholds State's Controversial Voter ID Law