A judge has temporarily blocked a controversial Wisconsin law that curbs collective bargaining rights for public employee unions.

The temporary restraining order is based on questions about the procedure by which the bill was passed, rather than upon the substance of the law itself.

Senate Republicans used a parliamentary maneuver to pass the law while Democrats were out of the state, trying to block a vote. Critics say the Republicans failed to give advance notice of their meeting, violating the state's open meeting law that requires 24-hours advance notice of legislative meetings, or 2 hours in an emergency.

The judge's order blocks the secretary of state from publishing the law, thus making it officially effective, until the legality of the bill's passage is examined.

The law was scheduled to be published on Friday, March 25.