This year the labor movement begins a long-dreaded, yet long-overdue day of reckoning at the high court. After a brief reprieve with the death of archconservative Justice Antonin Scalia, the Supreme Court’s brand-new Trump-approved conservative majority will take up the case of Janus v. AFSCME, and perhaps decide how public-worker unions operate for generations to come.

The central question in Janus—concerning fees paid by workers represented by a public-sector union—isn’t new. The current system of compelling all workers covered by a union contract, even if they are not formal union members, to contribute a “fair share” fee to support the collective-bargaining process was decided only in the late 1970s with a case called Abood v. Detroit Board of Education. These so-called fair-share fees, along with union members’ dues, have historically been seen as a basic source of funding for managing the process of collective bargaining for the workforce, and all workers in a bargaining unit are expected to contribute toward maintaining the union’s basic function. The case challenges fair-share payments as tantamount to “political” messaging, rather than a mandatory maintenance fee, which labor advocates say would effectively undermine the financial core of many public-*sector unions and weaken their membership and bargaining power.

However, in the 40 years that have since passed, the steep decline of private-sector unions and the simultaneous emergence of the public sector as the most strongly unionized segment of the workforce have made the stakes for the case against agency fees that much higher. Unlike previous legal challenges, such as the Harris v. Quinn case involving Illinois home-care workers, the Janus case centers on the First Amendment. The central argument is that fees required of workers in a collective-bargaining unit amount to a form of compelled political “speech” to the government, which should be considered a violation of the worker’s First Amendment rights. School worker Mark Janus was not a union member, and objected to being obligated to contribute a fair-share fee, even though he benefited from the union’s contract anyway. The case turns on the assumption that, whether you’re a teacher seeking smaller classes or a retiree seeking decent health care, the Court will essentially treat your union’s contract demands as ideologically lobbying your government.

Unions see Janus (along with a similar case, Friedrichs v. California Teachers Association, that was narrowly avoided under Obama) as a “frontal assault” on labor based on the “right-to-work” concept, using a distorted interpretation of free speech to undermine the financial and institutional structure of public-sector unions. Unions have long argued that there is a clear legal line separating lobbying and activities related to managing the basic contract-negotiation process. The First Amendment case in Janus is just a fig leaf for a right-to-work agenda. In the private sector, right-to-work legislation, already enacted in nearly half of states for private-sector workers, effectively preempts “closed-shop” unionization by allowing workers to opt out of union membership and financial obligations of their own free will. The parallel attack on civil-service unions similarly threatens to destroy the legal foundation of public-worker collective bargaining under state law.

While anti-labor libertarians will argue that all union activity is inherently “political activism,” unions maintain, with 40 years of evidence to back them up, that agency fees simply help them carry out critical duties as workers’ representatives, and that all who benefit have a responsibility to pay. As the New York City Municipal Labor Council argues in a brief, with the collective-bargaining representatives managing the needs of hundreds of thousands of workers, navigating issues ranging from pensions to parental leave, “The simple truth is that someone must contribute to permit the union to perform its job and if all who benefit cannot be required to contribute, union members would be forced to carry the weight on their backs, subsidizing those who free-ride.”

For unions, it’s not about an individual union detractor’s free speech but about the necessary and lawful right of workers to free association. For rank-and-file workers, securing a well-managed collective-bargaining process is an issue of economic justice. The Economic Policy Institute points out that the public sector serves as a bulwark of economic stability and equity for black women, who make up 18 percent of public-sector employment. Weakening state collective-bargaining systems would basically weaken a 1.5 million-strong community of black women workers nationwide in schools and government agencies.

Even state employers like the current negotiation system. California Attorney General Xavier Becerra contends on SCOTUSBlog that given the complexities of bargaining with large state workforces, “state collective-bargaining regimes provide public employers with a mechanism for effective personnel management.”

The Janus case doesn’t relate directly to the activities of private-sector workers, which are based on a separate precedent in private labor law. But according to Georgetown labor historian Joseph McCartin, if the court follows the right-to-work idea to “categorize everything public employee unions do as inherently political activity,” the labor movement as a whole could face a neoliberal boomerang effect for workplace democracy.

For over a century, public and private sector labor relations have had a symbiotic relationship with each other: union security in one sector tended to beget union security in the other, union insecurity in one sector tended to beget union insecurity in the other…. The erosion of private sector unionism since 1980 opened the door to a growing “right-to-work” movement and the legal assault public sector labor relations that has now culminated with Janus. The attack on public sector unions might in turn threaten private sector union security.

Nonetheless, while many union organizers fear the loss of revenue and members under an unfavorable ruling, which seems exceedingly likely now that Justice Gorsuch is seated, others predict that unions are strong enough to stand on their own terms if they do right by their members. If they lose Abood’s legal fallback, labor will then be challenged to mass organize to give workers a reason to see their unions as something worth joining, rather than a fee-collecting bureaucracy

Amherst professor Dan Clawson argues in an American Sociological Association symposium that Janus isn’t necessarily a death blow for labor but an opportunity, not only to defend union turf but to grow with renewed vigor:

Our ability to build a strong sense of what the union is and why it matters will determine our strength going forward. We are emphasizing that when people stay in the union that builds our collective solidarity and ability to win on the issues that matter to all of us; when people leave that hurts all of us.

The case for why workers and unions need each other is a more complex question than the legal issue before the Court—but ultimately the most important argument unions have to make. Outside the courtroom, at work, the real test for labor is not about the definition of free speech, but about the meaning of solidarity.