The Republican-majority Michigan legislature has given its final approval to "right-to-work" restrictions on public sector unions in a state considered a stronghold of organised labour.
Protesters chanted in the gallery and thousands rallied outside the building on Tuesday as the House passed the measure which makes membership and payment of union dues voluntary for public sector employees such as teachers by a 58-51 vote.
The Senate approved the same bill last week so it will now go to Republican Governor Rick Snyder, who has promised to sign it into law.
The public sector law was the first of two also expected to be approved by the House on Tuesday. The other covers private sector workers, including the large car industry in Michigan.
Al Jazeera's John Terrett, reporting from Lansing, Michigan, said there was little expectation that the second part will not pass.
"Michigan will become the 24th US state to adopt the so-called Right to Work Act, which essentially ends the practice of the closed shop, where someone has to belong to a union to accept a job offer," said Terrett.
More than 12,000 workers from throughout Michigan and the US Midwest protested as the legislature voted, gathering outside the building in freezing temperatures and a light snow to show their displeasure.
Gene Adamczyk , Michigan State Police Inspector, said the Capitol was closed to visitors when it reached capacity of 2,200. An estimated 10,000 people demonstrated outside.
A few protesters were ejected from the Capitol after they chanted slogans from the gallery during the debate.
Outside of the building, protesters tore down two tents set up for supporters of right-to-work as the crowd applauded, but Adamczyk said there had been no arrests by late morning.
The show of force by unionised workers recalled huge rallies in Wisconsin two years ago when Republicans voted to curb public sector unions.
The right-to-work movement has been growing in the US in recent years.
Indiana earlier this year became the first state in the industrial Midwest to approve right-to-work and several other states are watching the Michigan action closely.