MADISON (Reuters) - A Wisconsin judge will hear a legal challenge this week to the state's new controversial voter photo identification law.

Lawyers for The League of Women Voters, which says the measure violates the state constitution by disenfranchising eligible voters, present oral arguments against the law in a Dane County Circuit Court on Thursday.

Their lawsuit is asking the court to block implementation of the law, passed by a Republican-controlled legislature last year. It requires voters to present identification such as a driver's license at polling places for federal, state and local elections.

The suit argues the state constitution allows only convicted felons and mentally incompetent people to be excluded from voting.

The new law creates a third class of people, those who do not have identification, and would largely affect minorities and the elderly, the suit says.

Supporters of the law, which is set to be in full effect in time for the November presidential vote, say it is necessary to ensure the integrity of elections.

They note that the measure requires the state motor vehicles department to waive the $28 fee for state IDs for people who are obtaining them to vote.

But the lawsuit says to get the free state ID, voters must present the motor vehicles department with a birth certificate, passport or other documentation, none of which are free, and so the requirement represents an illegal poll tax.

Thirty states require voters to show some form of ID before voting, according to the National Council of State Legislatures.

In 14 of those states, including Wisconsin, the ID must include a photo.

The voter ID measure was part of a raft of legislation backed by Republican Gov. Scott Walker that triggered mass protests in Madison last winter and prompted a fierce political backlash from Democrats and union supporters.

(Editing by James B. Kelleher and Ellen Wulfhorst)

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