As of Tuesday, Michigan is now the 24th right-to-work state in the U.S. “Right-to-work” essentially means banning mandatory union membership from  workplaces, and for a state that’s known for its organized labor in the auto industry, this law will have a big impact. Michigan has the fifth-highest percentage of workers who belong to unions in the country—17.5 percent.

Michigan’s Republican-dominated House of Representatives approved a pair of bills—for private and public sector unions—on Tuesday, as more than 12,000 union workers and supporters protested in the state capital of Lansing. The protests turned ugly when the police got involved, donning riot gear, and in at least one case, using pepper spray to subdue the demonstrators.

For his part, Republican Governor Rick Snyder signed the bills into law as soon as they crossed his desk, and they are expected to take effect sometime in April. “I view this as an opportunity to stand up for Michigan’s workers, to be pro-worker,” Snyder said in a press conference afterward.

Supporters of the bills extol the choice they offer laborers of joining a union or not, and claim that more flexibility will be good for business. Opponents argue that these bills will reduce union membership and undermine unions’ ability to collectively bargain with employers for things like better wages and working conditions.

The right-to-work push by lame duck Snyder is seen, at least in part, as an attempt to weaken the Democratic Party in the state. Unions have traditionally been a major source of grass-roots support for liberals. The Atlantic predicts that this skirmish in Michigan is foreshadowing of future labor battles in other states such as Wisconsin, Ohio and New Jersey, where the 2014 gubernatorial races may shape the future of unions.

Read more about right-to-work laws on InsideCounsel:

Right-to-work bill advances in Indiana

Ohio group seeks right-to-work amendment

Union sues to block enforcement of Indiana right-to-work law