In the 2012 case Knox v. Seiu, the Supreme Court went out of its way to cast doubt on one of the key supports for strong public-sector labor relations in this country—namely, fair-share representation fees. These fees—which pay only for shared representation costs, not political activity—are collected from all employees if a majority choose union representation. Union members pay the fee as part of their dues; nonmembers pay just the fee.

Again and again over the last half-century, the Supreme Court has upheld fair-share fees. In its seminal 1977 decision in Abood v. Detroit Board of Education, the conservative Burger Court unanimously upheld such fees in the public sector, based on precedents allowing them in the private sector. And the Supreme Court and lower courts have repeatedly relied on Abood to uphold not just public-sector fair-share fee arrangements but other common collective fees as well, such as integrated legal-bar dues and student activities fees.

The legion of resulting decisions reflects the common-sense understanding that every employee who benefits from a negotiated contract should contribute to the costs of securing that contract. No one is forced to join a union, but unions are legally required to represent all workers—even those who decide not to join. Educators and public employees who don’t want to belong to a union only have to contribute to the costs of the representation they receive. Every public employee who benefits from a negotiated contract should contribute to the costs of securing that contract. The current fair-share system is a good compromise that eliminates the unfairness that would result if some people had to pay more than others for representation, or if some people received benefits for free.

But that common-sense solution was seriously questioned by the majority in Knox. Although the technical question presented could have been answered without addressing Abood, the majority went out of its way to paint that ruling—a precedent that has been followed, cited, and relied on hundreds of times—as an “anomaly,” a decision that “approach[es], if [it does] not cross, the limit of what the First Amendment can tolerate.”

Not surprisingly, the Supreme Court’s newfound doubts about Abood prompted pundits to proclaim that the Court had taken a turn to the right. Writing in The American Prospect, legal scholar Garrett Epps said that Knox was “the Court’s Scott Walker moment.” Tying the decision to the recent surge of right-wing legislative initiatives—including Wisconsin’s notorious Act 10, which limited the power of public employees to bargain collectively—Epps wrote that “the conservative majority on the Supreme Court delivered an unsubtle warning to public employee unions: You are living on borrowed time.”

And, of course, the Knox decision poured fuel on pending cases. One of those was Harris v. Quinn. Brought by the National Right to Work Legal Defense Foundation, Harris challenged an innovative Illinois statute akin to those enacted by nine other states, which all told gave a million home-healthcare aides a collective voice at work. The statutes reflected a cost-effective solution to the growing needs of elderly and other residents. By enabling them to remain at home rather than being institutionalized, these statutes saved the states hundreds of millions of dollars. That solution was possible because the bargaining process created by the statutes allowed the states to identify and address the common concerns of home-healthcare aides, which in turn reduced turnover, increased the quality of care provided, and boosted their wages above poverty levels.

Although the lower courts upheld the Illinois statute, the fortunes of the National Right to Work Legal Defense Foundation changed once the case reached the Supreme Court. After deliberating for more than a year over whether to even take the case, the Court struck down the statute in June 2014. And while questioning Abood was unnecessary to Harris’s resolution, the conservative justices once again seized the opportunity to take a series of what the dissenters aptly termed “potshots” at Abood’s reasoning. As Justice Elena Kagan famously summed up the result, readers of Harris “will know that Abood does not rank on the majority’s top-ten list of favorite precedents.… Yet they will also know that the majority could not, even after receiving full dress briefing and argument, come up with reasons anywhere near sufficient to reverse the decision.”

Friedrichs v. California Teachers Association, which the justices will decide this year, will give the Court another chance. Brought by the Center for Individual Rights, a conservative legal group, Friedrichs asks the Court to overrule Abood entirely, on the theory that the First Amendment prohibits fair-share fees altogether—or at least prohibits their collection through an opt-out system. Although the group is challenging a California statute that applies to public schools, the law is no different from the scores of statutes enacted by other states and localities that permit the collection of such fees in support of strong collective bargaining. If the Court accepts the plaintiffs’ arguments in Friedrichs, all of these statutes, and the tens of thousands of agreements founded on them, will be placed in jeopardy.

Buoyed by Knox and Harris, the Friedrichs plaintiffs clearly think their moment has come. They were so anxious to get their case to the current Supreme Court that they repeatedly asked the lower courts to rule against them as quickly as possible, so as to give the Roberts Court the opportunity to decide the case.

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What hangs in the balance is not just Abood and the decades of precedents that rest on it, but one of the few remaining ways for working Americans to band together and get ahead. In an economy that is increasingly and seriously out of balance, in which record wealth has made the richest richer than ever before but left ordinary people out in the cold, strong and effective collective bargaining allows teachers, firefighters, and nurses to join together and work for better schools and public services, and for fairer wages and benefits.

Over the last century, our nation’s commitment to collective bargaining—allowing employees to unite and have a voice in their workplace—has served this country well, creating the middle class that has powered our democracy. And the types of laws challenged in Friedrichs have both improved our public schools and opened the doors of opportunity to people of color, women, and immigrants. The Court should reject the invitation in Friedrichs to slam that door shut.