Paul Sancya, Associated Press
Rev. Al Sharpton speaks to the media in Detroit, Thursday March 28, 2013. Opponents of Michigan's new emergency manager law are seeking to block it in federal court, saying the measure is unconstitutional.

DETROIT — A lawsuit filed Thursday wants to stop Michigan's new emergency manager law, claiming it is unconstitutional and violates the federal Voting Rights Act.

The suit was filed on the day Public Act 436 took effect by a coalition of labor unions, clergy, elected leaders and residents from several cities in U.S. District Court in Detroit. Gov. Rick Snyder and Treasurer Andy Dillon are named as defendants.

The suit is the latest opposition to the state's emergency manager law, under which state-appointed emergency managers are given fiscal authority over cities and public school districts deemed to be in financial emergencies. The law also allows managers to modify or throw out union contracts and maintain automatic pay cuts for elected mayors, city council and city commission members and school boards.

Voters in November defeated an earlier law in a ballot referendum. The new law was passed by the state Legislature and signed in December by Snyder.

"That's just part of democracy and the process," Snyder said Thursday in Detroit when asked about the lawsuit. "When you have actions like this, people are going to file lawsuits. But our track record is very strong in winning those lawsuits.

"We'll go through the normal legal process. When they file lawsuits, I leave it to legal counsel and the attorney general's office to take them," Snyder said.

Civil rights leader the Rev. Al Sharpton announced the lawsuit Thursday on behalf of the local chapter of his National Action Network.

The lawsuit asks the court to declare that the law violates the U.S. Constitution and Voting Rights Act. It also wants the court to prevent emergency managers from implementing or exercising authority and powers under Public Act 436.

"This is an issue that has national ramifications," Sharpton said. "If they get away with it here in Michigan, it can be a model across the country that you can suspend elections."

Six Michigan cities and three school districts have emergency managers. Detroit became the latest when turnaround specialist Kevyn Orr started work Monday. Orr, a Washington-based bankruptcy attorney, helped lead Chrysler LLC through its bankruptcy.

Associated Press writer Mike Householder in Detroit contributed to this report.