The American labor movement currently stands at one of its lowest points in history. Barely one-tenth of all workers belong to a union—down from more than one-third in the 1950s. Over the past half-century, the courts have gutted legal protections for striking workers, curtailed their ability to engage in political action, and granted employers broad “free speech” rights to frighten them out of unionizing. Under President Trump, workers are likely to be besieged by even more hostile attacks from Republicans and their corporate allies—including calls for a national “right to work” law that would strip unions of their ability to collect dues. If the labor movement hopes to survive in the twenty-first century, it will need a new strategy.

For more than 80 years, workers have primarily relied on protection from the National Labor Relations Act, the landmark measure passed under FDR that prohibits unfair labor practices and encourages collective bargaining by private-sector employers. But the law has been so watered down by unfriendly court decisions and legislative amendments that it offers little recourse for the labor movement going forward. Today, according to a new report by a leading think tank, workers would be better off if they adopted a strategy that turned to a different and more sacrosanct set of constitutional guarantees: the Bill of Rights.

According to Shaun Richman, a former organizing director for the American Federation of Teachers, workers should not just defend their rights as employees, but should also start championing their liberties as citizens. In a report for the Century Foundation, Richman argues that just as corporations have gone to court to claim broad constitutional protections, workers should assert their fundamental rights to free speech and equal protection under the law. “Unions have rarely if ever argued that these cases violated their own constitutional rights,” Richman says. “Rights-based rhetoric was kept out of their whole legal strategy.”

Consider several recent cases that unions argued—and lost—under the National Labor Relations Act. In 2011, workers at a Jimmy John’s sandwich franchise in Minneapolis launched a campaign to protest the company’s refusal to provide paid sick leave. In response, the company fired six workers involved in the protest. But when the union representing the employees, the Industrial Workers of the World, accused the company of violating the National Labor Relations Act, a federal appeals court ruled in July that the company had the right to fire its employees for engaging in “disloyal” conduct.

At the same time, Congress and the courts have sharply curtailed the ability of workers to go on strike, especially in solidarity with others. It is now illegal for truck drivers to refuse to make deliveries to stores where workers are on strike, or for cleaners to refuse to wash linens from hotels where workers are protesting. In 2006, Roger Toussaint, then the president of Local 100 of the Transport Workers Union, was sentenced to ten days in jail for leading a transit strike that crippled New York City. Employers, meanwhile, have retained the right to lock out workers who are engaged in collective bargaining, and to fire employees without just cause.