(ABC NEWS) -- Michigan's Republican-controlled state legislature approved a controversial right-to-work bill Tuesday by a vote of 58-51. The bill now moves to Republican Gov. Rick Snyder's desk, where he is expected to approve it as early as Wednesday.
Michigan's law would make the payment of union dues voluntary for private-sector unions and most public-sector unions (police and firefighters would be exempt).
In anticipation of the vote, thousands of protesters descended on the statehouse in Lansing today, demonstrating their opposition to the bill both inside and outside the Capitol building. Demonstrations also moved to the governor's main office as well which is officially titled the Romney building, after former Michigan Gov. George Romney (father of Mitt).
There's symbolism in the location. During his tenure as governor, Romney signed the first bills in the state that gave collective bargaining rights to public-sector employees.
Demonstrators engaged in what labor officials termed "peaceful civil disobedience," linking arms to block entrances while chanting and singing. But there were bursts of violence as well. Michigan state police told the Associated Press that pepper spray was used to calm a protester, but there was no arrest in that incident. Two separate arrests occurred on Tuesday when two individuals tried to get into the Romney building.
Although Michigan will become the latest in a string of states to pass similar legislation- 23 other states have passed right-to-work laws- the passage of a such a law in union-heavy Michigan is particularly divisive in the state. Michigan is the birthplace of the powerful United Auto Workers organization and union representation in Michigan is among the highest in the nation; roughly 17.5 percent of the state's labor force is unionized.
If Snyder signs the bill, as he has indicated he will do, it will still be possible to put it on the ballot in 2014, when Snyder is expected to run for re-election. The bill includes appropriations, which means that it will automatically become law if signed, but the state constitution allows for voters to invoke a referendum to "approve or reject" the law.
Opponents of the law will have 90 days after the legislature adjourns to gather 8 percent of the total votes cast in the last gubernatorial race, which were more than 3 million.
If they succeed, the law will be placed on the ballot and subject to a statewide vote.