Updated

A law enforcement union filed a lawsuit Tuesday challenging the constitutionality of a Wisconsin law effectively ending collective bargaining for most public workers.

The lawsuit brought by the Wisconsin Law Enforcement Association seeks to strike down the law, championed by Republican Gov. Scott Walker, as a violation of constitutional rights of free speech, association and equal protection. While state troopers and motor vehicle inspectors were exempted from the law, University of Wisconsin officers, Capitol police and Department of Transportation field agents were not.

Attorney General J.B. Van Hollen's spokeswoman Dana Brueck issued a statement saying the complaint was under review.

"We believe (the law) is constitutional, and that we'll ultimately prevail," she said.

The lawsuit comes less than two months after a Dane County judge ruled the law unconstitutional as it applies to school district and local government workers. That ruling came in a case brought by Madison teachers and Milwaukee city workers. It did not apply to state workers. Van Hollen is appealing that ruling.

The new lawsuit filed in Dane County Circuit Court challenges the law as it pertains to law enforcement officers who had been represented for collective bargaining purposes by the Wisconsin Law Enforcement Association.

The law, which applies to nearly all public workers, allows collective bargaining only for base salary increases no greater than the rate of inflation. Collective bargaining over other issues, such as workplace safety, hours and job security, is not allowed.

It also required workers to pay more for their health insurance and pension benefits, a move Walker said was necessary to plug a $3.6 billion budget gap. It also did away with automatic union dues withdrawals and forced annual votes to keep unions organized.

Walker's opponents said his true intent was not to balance the budget but to quash public unions, a strong political force typically for Democrats.

The lawsuit points out that the two groups exempted from the law -- state troopers and inspectors -- are represented for lobbying purposes by the Wisconsin Troopers Association, which endorsed Walker in the 2010 election. All other law enforcement groups represented by WLEA that did not endorse a candidate in the 2010 election were covered by the law.

The lawsuit said the law forced the WLEA to break into two parts, each with different rights.

The law was designed to retaliate against law enforcement WLEA members and restrict free speech rights "for the improper purpose of diminishing the law enforcement unions' political effectiveness," the lawsuit argues.

The lawsuit also contends that constitutional equal protection rights were violated by treating those represented by the WLEA differently than similarly situated employees.

The WLEA said in a statement that the law "fractured the union and the solidarity of its members, undermining their ability to join together and advocate for the best conditions to keep Wisconsin roads and communities safe."