President Barack Obama said he was “deeply disappointed” in the so-called “right-to-work” law signed Monday by Wisconsin Gov. Scott Walker.

The legislation bans contracts between employers and unions that require private sector workers to pay labor fees or dues, and is widely viewed by the left as a deliberate attack on organized labor. Wisconsin is now the 25th state with such a law on the books.

“It’s no coincidence that the rise of the middle class in America coincided in large part with the rise of unions – workers who organized together for higher wages, better working conditions, and the benefits and protections that most workers take for granted today,” the president said in a statement released late Monday. “So it’s inexcusable that, over the past several years, just when middle-class families and workers need that kind of security the most, there’s been a sustained, coordinated assault on unions, led by powerful interests and their allies in government,” the president continued.

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The bill is just the latest, controversial labor stance from Walker, who is considered a contender for the Republican 2016 presidential nomination and has appeared to shift his positions to the right on several key issues of late.

Close video Walker slashes union rights Gov. Scott Walker plans to sign the controversial Right to Work bill into law, hurting unions across the state. Ed Schultz and St. Rep. Peter Barca discuss. share tweet email Embed

According to The Washington Post’s Ezra Klein, the past success of “right-to-work” laws is due to a “triumph of framing.” ”They give you the right to refuse to pay union dues when you work for a union shop, even though you get the wages the union bargained for, and the benefits the union bargained for, and the grievance process the union bargained for,” Klein wrote in a 2012 column for the Post.

Meanwhile, President Obama has stood firm in his opposition to what he called a “new anti-worker law” on Monday. “Wisconsin is a state built by labor, with a proud pro-worker past. So even as its governor claims victory over working Americans, I’d encourage him to try and score a victory for working Americans - by taking meaningful action to raise their wages and offer them the security of paid leave,” Obama said Monday. “That’s how you give hardworking middle-class families a fair shot in the new economy - not by stripping their rights in the workplace, but by offering them all the tools they need to get ahead.”