In March 2014, Sean Caldwell went to the first Philadelphia rally for the Fight for $15, the national campaign to raise the minimum wage and to help fast-food workers — who earn one of the lowest median wages in the country — form a union for the first time. Caldwell, an Army veteran and college student, who was 35, had been working for nearly two years as a janitor on the early-morning shift at a McDonald’s in North Philadelphia. Four days a week, he cleaned frying vats, unloaded delivery trucks and mopped and restocked the restaurant. He made $8 an hour.

At the rally, Caldwell handed out fliers and held a cardboard sign that asked drivers to honk in support of “$15 and a union.” He saw himself on TV that night in news about the protest. About a week later, Caldwell arrived at work two hours late for his 6 a.m. shift, after having been with his daughter in the emergency room past midnight. He’d tried to call in to say he’d be late, but no one answered the phone and there was no way to leave a message.

In Caldwell’s experience, it wasn’t unusual for employees, including managers, to be late to work. Shortly after he got to the restaurant that morning, he was fired. A few days later, when he went back to return his uniform, he said, a manager handed him a stack of write-ups dating back months, for lateness and other minor infractions, which he had never seen before. She asked him to sign them. Caldwell refused, because he didn’t know whether they were accurate, and suspected he was being fired for his involvement with the union.

It’s against the law to fire workers for labor organizing. The Service Employees International Union, which backed the Fight for $15 and represents almost two million workers in health care and other fields, in 2014 took Caldwell’s case, along with the complaints of hundreds of other workers who thought they’d been penalized for participating in the Fight for $15, to the National Labor Relations Board for an investigation. The federal agency was created in 1935 as part of the National Labor Relations Act, the cornerstone of American labor law, which has a mandate to protect the rights of employees “to join together” to improve their wages and working conditions. In December 2014, the N.L.R.B. general counsel, an Obama appointee, grouped 60 of them for an initial trial against McDonald’s and its franchisees.

McDonald’s was the second-largest private-sector employer in the world as of 2015. Ninety-five percent of its American restaurants are operated by franchisees, a model that has allowed the company to distance itself from the 850,000 fast-food workers who wear the McDonald’s uniform. During the administrative law trial, which began in 2016, lawyers for McDonald’s argued, according to court filings, that their client bore no responsibility for Caldwell’s firing because he worked only for a local McDonald’s franchise called Jo-Dan.

The N.L.R.B. challenged McDonald’s’ premise, arguing that McDonald’s jointly employed Caldwell and helped undercut the Fight for $15. The N.L.R.B. presented evidence showing McDonald’s’ corporate employees helping franchisees, including Jo-Dan, fight off unionization. In emails and text messages, the company connected franchisees with a hotline for legal advice from the law firm Littler Mendelson, and circulated the names of pro-union workers. In Philadelphia, the regional director of employee relations for McDonald’s, Maggie Calabrese, wrote a memo about the firing of Caldwell and others, noting a call she had with the franchise operator, John Dawkins: “I shared with John the benefits of working with” an anti-union consultant that McDonald’s recommended, she wrote.

McDonald’s had another tactic at its disposal — delay. The company mounted objections to entering documents into the record and canceled hearing dates. The trial dragged on into 2017, and after Donald Trump’s inauguration, he appointed a new N.L.R.B. general counsel, Peter B. Robb, who has spent much of his career representing companies against unions. In January 2018, Robb unveiled a proposed settlement: About 20 workers, including Caldwell, would divide roughly $170,000 in back pay; McDonald’s would admit no wrongdoing; and Robb would reverse the initial position the N.L.R.B. had taken in bringing the case that McDonald’s should be treated as a joint employer of the workers at its franchises. This stance would make it nearly impossible for employees to band together to address problems in the workplace.

In July 2018, the judge at the trial, Lauren Esposito, rejected the settlement proposal, saying it was not reasonable “based on the nature and scope” of the case. Esposito concluded that McDonald’s was directly involved in suppressing union organizing because it had “formulated and implemented” the franchisees’ response to the Fight for $15. If the N.L.R.B. accepted Esposito’s findings, a union would be able to conduct a drive to organize McDonald’s workers across the country.

But the N.L.R.B., whose five members are nominated by the president to serve staggered five-year terms, had the power to overrule Esposito. With two Trump appointees in the majority, the board ordered the judge to approve the settlement by a vote of two to one. (A fourth board member didn’t participate in the decision; the fifth seat was vacant at the time.) One of the two N.L.R.B. members who overruled Esposito, William J. Emanuel, was a former partner at Littler Mendelson, the firm McDonald’s hired to give legal advice to franchisees, but declined to recuse himself. Trump’s chairman of the N.L.R.B., John F. Ring, whose former firm also advised McDonald’s on the Fight for $15, later issued an unprecedented report finding that each N.L.R.B. member could “insist on participating” in a case even if the agency’s own ethics officials said otherwise. In response to my questions about the case, McDonald’s sent a statement: “McDonald’s and its franchisees agreed to resolve the proceeding in a manner that provides 100 percent of the remedies that those employees were eligible to receive under the National Labor Relations Act.”

Trump’s N.L.R.B. has hamstrung union activism in other ways. In May 2019, the agency classified Uber drivers as independent contractors, diminishing their ability to unite to demand better pay. It has also proposed a rule barring graduate students from forming unions.

The rulings are an indication that for tens of millions of low-wage workers, in sectors like fast food and the gig economy, American labor law is utterly deficient. If the N.L.R.B. can undermine vulnerable employees when they try to unionize, what does the law’s promise — to protect the rights of workers to come together — really mean?

The National Labor Relations Act, signed by President Franklin Delano Roosevelt in 1935, was a response to corporate behavior during the Great Depression. As unemployment deepened in the early 1930s, companies used their leverage to break unions — by conditioning a job on a worker’s agreement not to join one, or hiring private security to threaten union leaders, or sending strikebreakers to interrupt picket lines. Union membership fell to around 2.5 million in 1933 from four million in 1920.

Hundreds of thousands of workers turned to massive strikes. In 1934, longshoremen paralyzed the ports of the West Coast for weeks, Teamsters and the police killed one another during a strike in Minneapolis and striking workers at an auto-parts plant in Toledo clashed violently with National Guardsmen and company police. The strife was a challenge for Roosevelt and the Democratic Congress. At first, two longtime social reformers, Secretary of Labor Frances Perkins and Senator Robert F. Wagner, a Democrat from New York City, counseled the unions to be patient and negotiate. But in 1934, Wagner went to Virginia in hopes of using his personal influence to settle a strike at a textile plant and came back “breathing wrath” at the plant’s owners, according to Perkins’s memoir. “We’ve got to have a law that requires them to deal with the union in collective bargaining,” he told her. “Just imagine, they won’t even talk with the union.”

The N.L.R.A. forced employers to the bargaining table by giving workers the right to collectively bargain. Along with investigating companies for interfering with organizing, the N.L.R.B. would hold elections for unions and certify them when they won.

But from the start, the law had limitations as a tool for protecting workers. To win the votes of white Southern Democrats in the Senate, Roosevelt and Wagner agreed to exclude farmworkers and domestic laborers — nannies, cooks, house cleaners — many of whom were black, from the N.L.R.A.’s guarantees. More broadly, the law’s purpose, stated in its preamble, was “to diminish the causes of labor disputes burdening or obstructing interstate and foreign commerce” — in other words, to make peace between labor and business, not fundamentally alter the economic or political relationship between them. Unions could not organize across an industrial sector but had to do so company by company. Labor federations were given no role in setting wages, as some do in European countries.

For a dozen years, however, the N.L.R.A. was an engine for organizing American factories. Within months of the law’s passage, a new coalition, the Congress of Industrial Organizations, mounted a massive campaign of sit-ins and walkouts and succeeded in establishing unions with clout across the auto, steel and garment industries. Unions increased their membership to a high point of 35 percent of American workers in the mid-1940s.

Then big business hit back. In 1947, over President Harry Truman’s veto, Republican majorities in Congress passed the Taft-Hartley Act, which amended the N.L.R.A. by effectively permitting employers to use work time for mandatory anti-union meetings, banning sympathy strikes and boycotts and allowing states to pass right-to-work laws, which ban mandatory union dues for workers even though they are benefiting from a union’s representation. The last change is a big blow to labor’s political power because it reduces union membership and revenue.

For decades, though membership began to decline, unions held their own in an economy that still centered on U.S.-based manufacturing. They also expanded into the public sector. In the 1970s, 1,000 workers or more participated in each of nearly 300 strikes a year. But in a warning of labor’s waning power, a major push to stiffen the penalties for companies that violate the N.L.R.A. died in a Senate filibuster in 1978, blocked mostly by Republicans as well as a few Democrats. That was also the last year in which unions were able to match the campaign donations of businesses to congressional elections.

American workers took a beating in the 1980s — “labor’s witching hour,” as Steven Greenhouse, author of the 2019 book “Beaten Down, Worked Up” and a former longtime New York Times labor reporter, puts it. The event that set the stage for crippling unions began with a strike by federal air traffic controllers in August 1981. President Ronald Reagan declared their action illegal and fired more than 11,000 striking workers, hiring replacements. In October, the government decertified the union, which disbanded. One of the Reagan administration’s lawyers in the case was Peter B. Robb, now general counsel of the N.L.R.B.

The law the Reagan administration relied on had been on the books since 1955, but over the course of 39 previous work stoppages, no president had used it to fire federal workers. When more than 150,000 postal workers went on strike in 1970, for example, the Nixon administration didn’t retaliate against them, and they won a big raise. But once a popular president busted a union, private-sector employers saw new opportunity. “By showing the way, Reagan invigorated the militant efforts of business to break strikes,” Joseph A. McCartin, a labor historian at Georgetown University, told me. As the president of the Phelps Dodge Corporation, a copper-mining and smelting company, said after hiring more than 1,300 replacement workers to defeat a long strike in 1983: “Suddenly people realized, Hell, you can beat a union.”

Unions struggled to adjust to the hardball strikebreaking tactics just as a cascade of forces — deregulation, the outsourcing of factory work abroad and corporations’ increasing focus on maximizing shareholders’ wealth — ate away at workers’ job security. The N.L.R.A. was unequal to the task of protecting them. When workers voted to start a union, it became routine for companies to contest the validity of the results, delaying certification for years. When the N.L.R.B. sided with workers, as it continued to do during Democratic administrations, the main remedy it could offer — back pay — was too small to have a lasting deterrent effect. “Researchers have found that nearly 20 percent of rank-and-file union activists are fired during organizing drives,” Greenhouse writes in his book. “It’s almost foolhardy for anti-union companies not to fire the two or three workers heading an organizing drive.”

These dynamics help explain why the share of workers who belong to a union has fallen to about 10 percent, the lowest rate of any wealthy country, even though public approval of unions has risen to 64 percent in the past decade, according to Gallup. As unions go, so goes inequality. The division of income among Americans has increasingly tilted to the richest 10 percent, and away from everyone else, as union membership has ebbed.

This month, Democrats in the House passed a bill to broaden the right of employees to organize and strike to include independent contractors, who number between 10.5 and 15 million, and to increase the penalties for companies that violate the N.L.R.A. In January, Clean Slate for Worker Power, a coalition of more than 70 participants from labor, academia and nonprofit organizations brought together by Harvard Law School’s Labor and Worklife Program, released proposed reforms that would extend the N.L.R.A.’s protections to agricultural and domestic workers as well as independent contractors and also give all workers a say in how companies are run.

One of Clean Slate’s most sweeping recommendations is for sectoral bargaining, which is common in Scandinavia, and makes it legal to negotiate a contract across an industry rather than one company at a time. There’s a potential competitive benefit for businesses: If McDonald’s, Burger King and Wendy’s agree to pay the same wages and benefits, one can’t gain an advantage over another. In a sense, the Fight for $15 has achieved a broad version of it in some blue states. Since 2016, California, Massachusetts, New York, Maryland, New Jersey, Illinois and Connecticut have enacted minimum-wage increases for all workers to $15 an hour, phased in over time. So have more than 15 cities, including Los Angeles, Seattle and St. Paul, Minn.

But there’s little pressure for corporations to accede to labor’s demands; in the 2016 election cycle, businesses outspent unions by a ratio of 16 to 1. To change the law, unions have to increase their political power in spite of all the obstacles. Héctor Figueroa, a respected labor leader in New York City who added 50,000 members to his chapter of the S.E.I.U., criticized his own movement, in a July 2019 Op-Ed in The New York Times, for failing to put sufficient resources into expanding its ranks and building new sources of power. Figueroa noted the problems for labor caused by the weakness of the N.L.R.A.: “But there’s plenty of blame to go around,” he wrote. “We have let ourselves be backed into a corner, by trying to just hold on to what we have.” (Figueroa died that July.)

In the past couple of years, a new burst of organizing has succeeded by reviving an old weapon — the strike. In her new book, “A Collective Bargain,” the organizer Jane McAlevey describes the strategic preparation behind the Los Angeles teachers’ successful strike in early 2019. The teachers built support among parents. They prioritized “community demands”: reductions in class size, green spaces for schools and an immigrant-defense fund for undocumented families.

In McAlevey’s vision, educators and health care workers, “mostly women and women of color, different from the guys in the factories,” can build the organizing capacity and leverage to transform American politics. Could teachers and nurses achieve what steel and autoworkers did in the 1930s? “We didn’t get the N.L.R.A. without a massive crisis on the streets,” McAlevey says. “That comes first. Then you get to change the rules.”

McCartin, the Georgetown historian, also sees the “militant re-emergence of workers” as a precondition for turning around the labor movement’s losses. “Remember, the N.L.R.A. wasn’t even on the wish list of a president like Roosevelt,” he said. “He came through because he saw that he had to.”

All Part of The Future of Work

Emily Bazelon is a staff writer at the magazine and the author of “Charged: The New Movement to Transform American Prosecution and End Mass Incarceration,” which is a 2020 finalist for the Los Angeles Times Book Prize in the current interest category and the Helen Bernstein Book Award for Excellence in Journalism from the New York Public Library.