Wisconsin unions sue over new collective bargaining law

Protesters return to occupy the state Capitol, as the Wisconsin State Assembly takes up the budget bill that was proposed from Wisconsin Republican Governor Scott Walker, in Madison June 14, 2011. War.

MADISON (Reuters) - Unions representing public workers in Wisconsin filed a lawsuit in federal court on Wednesday to block the state's new curbs on collective bargaining, which were upheld by the state's Supreme Court on Tuesday.

The lawsuit, filed in U.S. District Court for the Western District of Wisconsin, claims the controversial measure is unconstitutional because it creates two classes of public workers in the state -- those covered by the new rules and those exempt from them.

The law eliminates most collective bargaining rights for most Wisconsin teachers, road workers and other public employees and requires them to pay more for pensions and health coverage.

But certain public workers, including firefighters and other public safety workers, have been exempted from the new rules.

The suit argues that the differential treatment violates the constitutionally protected equal protection rights of the employees covered by the law.

The measure was passed in March by the Republican-controlled legislature and signed by Republican Governor Scott Walker.

It triggered the largest public protests in Madison since the Vietnam War and prompted a national debate over unions.

(Writing by James B. Kelleher)