It’s a common trope in US culture: people sitting in parks or on front porches drinking from bottles wrapped in brown paper bags.

What’s the point of that bag of paper? It forces a choice. A police officer who sees someone drinking from a brown bag must choose between investigating further and taking action or looking the other way. Critically, it’s the thinnest of veneers that provides the officer with enough plausible deniability to choose the latter. The officer didn’t see the label. They didn’t know what the person was drinking. And given that the officer had other more pressing priorities, they chose not to investigate any further.

To be clear, a brown bag over a bottle of alcohol is not an actual legal protection. Drinking in public in many places is a violation of open container and public intoxication laws. But there is still a valuable lesson here: enforcement is discretionary.

And the brown-bag tactic of plausible deniability extends beyond liquor and beer. It also applies to labor actions. And it is on full display right now as thousands of agents working for the Transportation Security Administration (TSA) are calling out sick in an organic, bottom-up wildcat partial strike that defies the government and the law.

Federal laws prohibit strikes by federal workers and can be extremely punitive. Federal workers who strike can face a felony prosecution, time in prison, and fines of thousands of dollars. In fact, if you are a federal worker, you can be officially blacklisted from working for the federal government just for claiming you have the right to strike or even for being a member of a union that makes that claim.

To win real collective bargaining rights, federal workers had to directly face off against these constraints.

It’s hard to imagine today, but there was a massive wave of public sector strikes in the 1960s and 1970s. Over those two decades, hundreds of thousands of public sector workers went on strike, often in defiance of their union and the boss. Postal workers won the right to collectively bargain in 1970 after two hundred thousand rank-and-file workers illegally hit the picket lines in the largest wildcat strike in US history. “Strikes, it’s safe to say, created the public employee labor movement,” wrote Joe Burns, author of Strike Back: Using the Militant Tactics of Labor’s Past to Reignite Public Sector Unionism Today.

Since the New Deal era, the growing norm in the United States, established and maintained through collective action, had been for the government to play nice: let the federal workers strike and intervene to force a settlement to the dispute. But the strike wave of the 1960s and 1970s came to a crashing halt in 1981 when negotiations over wages and working conditions broke down between the Professional Air Traffic Controllers Organization (PATCO) and the Federal Aviation Administration.

This was the era of Ronald Reagan and an ascendent corporate class. Even though PATCO was one of the only two unions that endorsed him for president, Ronald Reagan fired eleven thousand air traffic controllers and barred them from ever working for the federal government again. Bankrupted and decertified, PATCO was the first of many unions destroyed by the explosive employer offensive that was launched in this period.

Decades later, federal workers are still living with the consequences of Reagan’s attacks on organized labor, which is why so many federal workers will keep working, even under extreme conditions without pay. But everyone has their limits.

The fifty thousand TSA employees who administer the security in our nation’s airports have been working without pay since February 14, when a partial government shutdown went into effect as a result of a showdown between Democrats and Republicans over reforms to Immigration and Customs Enforcement (ICE) operations, such as mandating the use of signed judicial warrants and prohibiting agents from wearing masks. Hundreds of TSA agents have quit their jobs, but thousands more are simply calling out sick to work — in essence, they are engaging in a de facto nationwide partial strike. And since it’s not sanctioned by their union, it’s a wildcat.

For the last week, the TSA national call-out rate has been about 12 percent of the workforce, but at some high-volume airports that number is much higher: over 40 percent at both George Bush Intercontinental and the William P. Hobby Airports in Houston as well as Hartsfield-Jackson Atlanta International Airport and over 30 percent at JFK Airport in New York City. In these cities, the wait times to get through security can be anywhere from three to six hours.

Sick-outs are common labor actions used by public sector workers, especially by police officers, who are also often barred by local and state laws from striking and have dubbed this tactic the “blue flu.” Even though their actions are highly disruptive, TSA agents aren’t picketing in front of the airports, they didn’t take a formal vote to engage in these actions, and their unions haven’t called on their members to not report to work. Workers are maintaining the thin veneer of being sick — presumably sick of working for weeks on end without being paid — and like a cop on the beat faced with the paper bag, the federal government is choosing to look the other way.

“The PATCO strike was not a blue flu scenario, it was an explicit, organized strike by a federal workers union in defiance of the law because they thought their collective action would be sufficient. It wasn’t,” said Harris Freeman, labor and employment law faculty at the University of Massachusetts Amherst Labor Center. “What TSA agents are doing is guerrilla organizing. It’s asymmetric class struggle by workers against the federal government. And they are doing it with some level of success, because so far, there are no public threats of retribution by the federal government, and the general public is largely sympathetic of TSA agents for not showing up to work a job at which they’re not getting paid.”

Despite the massive inconvenience of standing in lines for hours on end, many people seem to be sympathizing with TSA workers — and heaving most of the blame on Congress and the White House. Local news stations around the country have provided anecdotal evidence for how people are feeling through man-on-the-street style interviews with travelers who have been standing in lines for hours.

“Pay TSA! It’s important to pay TSA!” exclaimed one traveler to CBS19 in Tyler, Texas. “I wish every senator, every congressman, could stand in this line,” said another.

Donald Trump has responded to the TSA brown-bag strike by deploying ICE agents to airports across the country, despite their lack of training and penchant for excessive force. Unlike TSA agents, ICE employees are being paid. And while there is no formal picket line, ICE agents are being used as temporary replacements. Or, in union parlance: ICE agents are now scabs.

Given their constraints, don’t expect to hear that kind of rhetoric coming from the unions that represent federal workers. But that doesn’t mean they don’t have sharp words about Trump’s deployment of ICE agents. Everett Kelley, American Federation of Government Employees president, which represents TSA employees, responded sharply, saying TSA agents “deserve to be paid, not replaced by untrained, armed agents who have shown how dangerous they can be.”