“Now the bosses are going to know that the workers have rights, too,” said Maria Garcia, a member of the labor group Arise Chicago, which spearheaded the campaign to pass the law. Interviewed in Spanish, Garcia said she’d experienced wage theft at both of the past two restaurants where she’d worked.

“Wage theft” encompasses a range of offenses. Garcia said that in her case, it had included unpaid overtime and hourly rates below the minimum wage. The term was popularized by labor activists seeking to stir moral outrage at the all-too common issue: “Wage theft” suggests that refusing to pay wages that workers have earned is a form of robbery, rather than a mere accounting dispute. Recent years have seen increasing traction for campaigns to strengthen wage theft penalties and remedies. Those efforts have also inspired a counter-attack: Last year, Florida Republicans and big businesses pushed a bill that would have overridden local wage theft measures. “We believe the existing court system is the best place for these claims,” a spokesperson for the Florida Retail Federation told the Huffington Post.

There’s serious money at stake. In 2008, the National Employment Law Project and a group of advocates and academics talked to around 4,000 low-wage workers in Chicago, New York City and Los Angeles. Two-thirds (68 percent) of the workers reported experiencing some form of wage theft in the past week. Researchers calculated that out of an already-low average $339 in weekly income, low-wage workers each lose an average of $51 weekly in wages they earned but never received. That adds up to over $56 million per week among workers in the country’s three largest cities.

Under Chicago’s new law, companies convicted of wage theft could have their business licenses revoked. Chicago Mayor Rahm Emanuel, no close pal of labor, signed on as a sponsor and has pledged to sign it (some of the same groups that have been collaborating with the mayor’s office on the wage theft bill have meanwhile been organizing furiously against the city’s decision to bring in a different janitorial contractor at O’Hare airport, which could eliminate 300 union jobs).

The major showdown over the new law occurred in committee hearings prior to Thursday’s vote. Adam Kader, the Workers Center Director for Arise Chicago, said supporters mobilized a “major show of force” from workers and community activists. Kader said opponents brought “a significant show of force by all of the major industry lobbyists in the state of Illinois.” But after agreeing to a change in the bill’s language, specifying that businesses could have their licenses revoked only after willful or egregious violations, labor was able to win over the council’s holdouts — though not the business lobbyists. (According to the Chicago Tribune, Alderwoman Emma Mitts, who chairs the relevant committee, last week said she was hearing from business leaders concerned that they would be unfairly punished for honest mistakes in how they calculated their workers’ pay.)

“In low-wage industries,” said Kader, “it’s standard practice to be practicing wage theft.” Now, he said, “there’s another force that they have to reckon with, which is the threat of losing their license.” Advocates say Chicago is now the second, and the largest, U.S. city with such a law on the books. San Francisco was the first.

Of course, on paper, refusing to pay workers the wages you owe them is illegal everywhere. So why does the problem persist? Part of the answer is anemic enforcement. A 2012 report from the Progressive States Network noted that the ratio of federal Department of Labor enforcement agents to U.S. workers has fallen from one for every 11,000 in 1941, to one for every 141,000 today. When state labor agents are factored in, the authors found “less than 15 percent of the total enforcement coverage workers enjoyed decades ago.”