The Michigan Legislature on Tuesday gave final approval to contentious "right-to-work" legislation, in the face of raucous protests in the capital and stern warnings from Democratic lawmakers.

"There will be blood, there will be repercussions," State Democratic Rep. Douglas Geiss, speaking on the House floor on Tuesday, warned ahead of the votes.

The final votes on the House side Tuesday deliver a blow to the labor movement in the heart of the U.S. auto industry. The measures ban unions from demanding dues from workers.

One bill dealt with public sector workers, the other with government employees. Both measures cleared the Senate last week, and were signed by Republican Gov. Rick Snyder on Tuesday afternoon.

Coinciding with the votes were massive and noisy protests both inside and outside the Capitol from pro-union demonstrators. Thousands descended upon downtown Lansing to rally against the legislation that prohibits requiring nonunion employees to financially support unions at their workplace.

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Earlier in the day, two state school districts closed after hundreds of teachers called out, presumably to join the protests.

FoxNews.com confirmed that the Warren school district had to close Tuesday after so many teachers called out absent; WDIV in Detroit reported that the Taylor school district had to do the same. A statement from the Warren system said that by 8 a.m. local time, 750 staff members had called out.

"Our decision to close school was based solely on student safety given the number of staff who called in absent today," the school district said in a statement.

Snyder, in an interview with Fox News, said it was "unfortunate" that teachers called out.

"Too often the educational system's all about the adults," he said. "To see schools shutting down because of an issue like this is not appropriate in my view."

Snyder, a Republican who is expected to sign the "right-to-work" legislation, defended his position.

"This is about giving workers the freedom to choose whether their resources go to a union or not -- and I actually don't view this as anti-union," he said. "Indiana's had a strong experience. ... They've seen thousands of jobs come to Indiana. Those jobs could also come to Michigan."

Several high-profile Democrats, though, have gotten involved, with Michigan Democratic Sen. Carl Levin and House Democrats meeting with Snyder on Monday and urging him to veto the bill.

President Obama also weighed in Monday, using a speech near Detroit to call out local Republicans.

"These so-called 'right-to-work' laws, they don't have anything to do with economics. They have everything to do with politics," Obama said. "What they're really talking about is they're giving you the right to work for less money."

The surprise move by Michigan Republicans last Thursday to approve the anti-union bills touched off a firestorm in the home of the U.S. auto industry. Following high-profile fights over union privileges in Wisconsin and Indiana, Michigan in an instant became the latest battleground in that struggle.

Though Republicans control the capital and had the votes all along to send the bill to Snyder's desk, opponents are planning to mount a legal challenge. Given the rapid manner with which the bills moved and the fact some demonstrators were kept out of the chambers, Democrats say they'll challenge under open-meetings laws.

The Detroit Free Press also reports that Democrats could try and challenge a provision that exempts police and firefighters.

However, any attempt to bring the proposal to referendum is complicated by the fact that the bill contained an appropriation -- and under Michigan law, appropriations bills cannot be challenged by popular vote.

In order to bring the "right-to-work" bill to referendum, supporters would have to first prove the appropriation to be somehow invalid or inappropriate.

Opponents could also launch recall campaigns against targeted Republicans in retaliation, as they did in Wisconsin following a vote that cracked down on collective bargaining.

Fox News' Mike Tobin and The Associated Press contributed to this report.