U.S. Supreme Court Chief Justice John Roberts. (Nati Harnik / AP)

We don’t officially celebrate International Workers’ Day on May 1 in this country, even though the worldwide holiday was originated to memorialize the Chicago Haymarket Square Riot of 1886 and the long and often bloody movement waged by American workers to establish the eight-hour workday. Instead, we hold a watered-down substitute, observing Labor Day on the first Monday of September. Each year, the commemoration grows more tepid and disconnected from the historical and current struggles of working people.

If the U.S. Supreme Court’s dominant Republican majority has its way when the panel’s new term commences in October, we might as well dispense with the holiday altogether, or at least drop the term “labor” from its title. Among the most important cases the court will consider when it reconvenes is Friedrichs v. California Teachers, which poses what some observers have called an “existential threat” to public unions and by extension to the entire labor movement.

At issue in Friedrichs is the right of public sector unions to collect limited “fair-share” fees in lieu of full formal dues from nonunion workers to defray the costs of collective bargaining that benefits all employees. A decision against the teachers association would have the potential to bankrupt government employee unions and turn the nation’s entire public sector into one enormous “right-to-work” jurisdiction.

Even before agreeing to hear Friedrichs, the Supreme Court under the leadership of Chief Justice John Roberts had amassed a staggering résumé of anti-worker decisions. As a study published in January by The Nation explains, the Roberts court has issued rulings that have restricted gender-based discrimination and class-action lawsuits against corporations; curbed age discrimination claims; limited the availability of overtime pay; redefined the term “supervisor” to allow employers to avoid liability for harassment; and made it more difficult for employees to prosecute workplace retaliation grievances.

Over the past few years, the court’s conservative majority has expressed a special animus against public employee unions, displayed not just in its interpretation of state and federal labor statutes but in a novel and twisted interpretation of the First Amendment. It’s complicated, but in a nutshell, the conservative legal theory works like this:

Under current law, no one can be forced to join a union, even one that has been elected by a majority of workers to negotiate on their behalf. In non-right-to-work states, however, unions nonetheless can collect mandatory fair-share fees from workers who want to keep their jobs without becoming union members. Typically, dissenting nonunion workers are billed for full regular union dues, but they have the right to “opt out” of making full payments, remitting instead only the fair-share fees that are needed to help the union meet expenses for collective bargaining. Fair-share fees (also called “agency” fees in reference to the union’s status as the sole agent authorized to act on bargaining) cannot be used to pay for other union expenses, such as contributions to political campaigns and most lobbying.

In a landmark 1977 decision dealing with government unions, one handed down during a more labor-friendly era in the court’s history—Abood v. Detroit Board of Education—the justices upheld the constitutionality of fair-share fee systems.

But the Roberts court, operating in a new era of hostile anti-worker judicial activism, has steadily chipped away at the Abood rule. Starting in 2012 with its opinion in Knox v. SEIU and continuing with its 2014 decision in Harris v. Quinn, the court’s five Republican appointees have emphasized that the payment of union dues by public employees is a form of political speech subject to the constraints of the First Amendment because public unions negotiate contracts with governmental entities and such contracts by definition affect public policies and the spending of taxpayer money.

The First Amendment, they reason (and here is where the twist sets in), protects not only the affirmative right to speak but also the passive right not to be compelled to speak or compelled to endorse the offending speech or acts of other people or groups. Requiring dissenting employees to pay fees to a union they don’t want to join, the analysis continues, amounts to such compelled speech in violation of the First Amendment. In the Knox case, the conservative justices took a big first step toward implementing their analysis in a class action brought by a group of dissenting nonunion state workers against California’s largest public worker group, the Service Employees International Union. The dissenting workers objected to a special midyear dues assessment that SEIU, Local 1000, had mailed to all employees (union and nonunion), imposing a small levy on their paychecks to help defeat two voter initiatives promoted by then-Gov. Arnold Schwarzenegger and the state’s Republican leadership. One of the initiatives, both of which had qualified for the 2005 California ballot, aimed at capping overall state spending, and the other required unions to obtain written approval from members before they could use the members’ dues for political purposes.

Although both initiatives eventually were defeated, and the local offered to refund the levy to nonunion members upon request, the plaintiffs persisted with their lawsuit all the way to the Supreme Court, where they found a receptive audience. In a majority opinion written by Justice Samuel Alito, and joined by Alito’s four Republican brethren, the court held that the midyear special assessment ran afoul of the First Amendment as to the nonunion members. Instead of being required to opt out of paying the special assessment after the fact and waiting for a refund, the court said, the nonunion workers should not have been required to pay the special assessment in advance. Rather, they should have been accorded the right to affirmatively consent, or “opt in,” to paying the assessment if they were so inclined.

Fortunately, Alito’s Knox opinion didn’t explicitly overturn Abood, and it left the traditional opt-out procedures for regular annual dues intact. In the Harris case two years later, in another 5-4 majority opinion penned by Alito, the court again came close to reversing Abood. The ruling came in a lawsuit involving an Illinois SEIU local brought by a group of home care attendants who did not want to join the union or pay fair-share fees. The court managed to sidestep Abood once more only by declaring that the home care workers were not really government employees and thus had no obligation to remit any kind of union dues.

The Friedrichs case presents Alito and his cronies with a third chance to do away with Abood and the entire mandatory fair-share system in the public sector nationwide, once and for all. The plaintiffs, including lead litigant Rebecca Friedrichs of Orange County, are 10 anti-union California schoolteachers and the Christian Educators Association International. Although the teachers are clearly government employees and reap the wage, retirement and health insurance benefits secured by union contracts, they oppose fair-share fees of any kind.

Unlike the plaintiffs in Knox and Harris, who were represented by the National Right to Work Legal Defense Foundation Inc., the Friedrichs group is represented by the Washington, D.C.-based Center for Individual Rights, an ultra-right-wing legal outfit that has made a name for itself in lawsuits opposing affirmative action, the Voting Rights Act and Obamacare, among other matters. Though the CIR handles much of its docket on its own, it has teamed up as co-counsel on Friedrichs with conservative super-lawyer Michael Carvin of the powerful Jones Day law firm.

But no matter who is directing Friedrichs, the aim of the case is the same as the goal previously sought in Knox and Harris—the crippling of public sector unions, both as bargaining agents for government workers and as sources of political funding and donations for liberal political candidates and campaigns.

It’s easy to understand the endgame that the American right is pursuing in such cases. Public unions are the last bastion of organized labor in America. According to the Bureau of Labor Statistics, the percentage of unionized wage and salary workers in the U.S. dropped to 11.1 percent in 2014 from 20.1 percent in 1983. The unionization rate in the private sector stands at an abysmal 6.6 percent. The public sector, by contrast, boasts a unionization rate of 35.7 percent.

If the recent labor strife in Wisconsin is any bellwether, a plaintiffs’ victory in Friedrichs could be disastrous. In the aftermath of Gov. Scott Walker’s 2011 assault on public unions and the state’s subsequent implementation of right-to-work policies, the declines in public union membership and dues collected have been enormous in Wisconsin, according to The Washington Examiner. The Madison local of the American Federation of State County and Municipal Employees has lost 18,000 of its previous 32,000 members and has seen its annual revenue fall from $10 million to $5.5 million.

The lesson thus is simple: Kill the fair-share regime and you kill public sector unions. Kill public sector unions and you kill off the labor movement as a whole.

Will the Supreme Court finally implement the lesson plan? We’ll know in the coming months.

From the Haymarket Riot to the present, it’s been a bumpy ride for American workers. In the meantime, I’m sure that Justice Alito and his black-robed compatriots will join me in wishing you happy Labor Day.