On Valentine's Day, an estimated 1,000 protesters gathered on the icy field of Independence Mall, waving flags and holding signs about immigrant rights. Most of them were Latino immigrants, some were Asian. They periodically chanted "Si Se Puede"—Yes We Can. Meanwhile, throughout the region, restaurants and scores of other businesses struggled to make do without their immigrant workers [Cover, "The Big Miedo," Doron Taussig, Feb. 9, 2006].

The immigrants were engaged in a paro -- a work stoppage in protest of the Border Protection, Anti-Terrorism and Illegal Immigration Control Act, a bill that, having already passed the U.S. House, could make it an aggravated felony to be, employ or assist an illegal alien. During the protest, organizers expressed satisfaction with the turnout, but Tuesday's events may reverberate well after debate over this particular bill has disappeared.

LABOR PAINS: Luis Hurtado was among the hundreds who turned out to oppose a bill before the U.S. Senate targeting immigrants for deportation. : Michael T. Regan

Protests that prominently involve illegal immigrants, as this one did, are rare. Until now, the idea of a mass of immigrants simultaneously skipping work has been mainly the domain of fiction—the movie A Day Without a Mexican (2004) made the scenario famous, but not real. Illegal immigrants tend to be reluctant to call attention to themselves; moreover, what would they tell their bosses? Because they are illegal, they have no leverage in negotiating with their employers.

What the organizers of Tuesday's event tried to do was change the status quo: They created leverage for undocumented workers. Ricardo Diaz, a spokesman for the group of activists who put el paro together, says there are several bargaining chips available to illegal immigrants. The first, and simplest, is labor: Employers need immigrant workers to keep their businesses afloat. For one worker, this is not a very valuable chip. But by mobilizing many immigrant workers at once, el paro created de facto labor unions. Many employers had to choose between cooperating with the stoppage or finding a new staff.

Most protesters said that their bosses had given them no trouble about taking the day, and several restaurant owners contacted by City Paper said that they supported their immigrant employees' cause. Diaz is harboring hopes that these employers will use their influence to fight the Border Protection bill.

But there were a recalcitrant few. A handful of owners, Diaz says, told their employees that if they didn't come in on Valentine's Day, they'd be fired. One restaurateur fired five people just for saying they planned to participate in the strike, and stuck to his guns even after the organizers reached out to him. For situations like this, Diaz is calling in the lawyers.

The owner in question, Diaz says, has failed to pay overtime, paid workers under the table and skimped on taxes—a slew of violations to which his workers can attest and which which would add up to thousands of dollars in fines. Historically, employers haven't worried about illegal immigrants reporting labor violations, assuming workers would be too frightened to go to the authorities—if they even knew which laws had been broken. But Diaz has enlisted attorneys to ask workers about the conditions of their workplaces, to "negotiate" with uncooperative owners and to go to authorities in the workers' place.

It hasn't come to that yet (Diaz declines to name the one restaurant, in the hope that the owner will come around). And of course, any employee who chooses to go to the mat in that fashion would be putting himself in danger. "Workers know the risk they're assuming," Diaz says. But there's a big difference between having the choice to assume that risk and feeling utterly powerless.

The power of this strategy was apparent in this week's turnout. Even before the protest, Diaz says, community leaders were calling him and asking, "What do we do after Tuesday?" Diaz isn't sure what to tell them yet. Could illegal immigrants join together to fight for higher wages, demand benefits, request amnesty? All he knows right now, he says, is that the phrase "life, liberty, and the pursuit of happiness" keeps running through his head.

Charles Kaing and Alexandra Zendrian contributed to this report.