The U.S. Supreme Court rejected an appeal to overturn Wisconsin’s voter identification law, upsetting civil rights and liberal groups that say the law discourages minorities from casting their ballot.

On Monday the justices said, without comment or explanation, that they would not hear an appeal aimed at overturning the voter ID law, which was signed into law in 2011 by Republican Gov. Scott Walker, a potential 2016 presidential contender.

The American Civil Liberties Union immediately filed a motion for a stay so as to not allow the law to go immediately into effect.

The ACLU challenged the law — which requires voters to present photo identification before they cast their ballots — saying it violates the 14th Amendment’s equal protection clause and Section 2 of the Voting Rights Act against discrimination in voting.

In a statement Monday, Mr. Walker praised the justices’ decision to let the law stand as “great news for Wisconsin voters” and “a common-sense reform that protects the integrity of our voting process, making it easy to vote and hard to cheat.”

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