The right to hire and fire these workers remains solely, of course, that of their home-bound patients and their families. The workers, then, are joint employees of both their patients and the state. And since the state allowed them to vote on whether to join a union, and since they voted to join the Service Employees International Union, these 28,000 workers have seen their pay doubled and have received, for the first time, health care coverage. Like all unionized public employees, they don’t have to pay that portion of their union dues that goes to their union’s political activities, but they do have to pay that portion of dues that goes to the union’s bargaining with the state that has produced their contract. The extent of and limits on their dues obligations were established in the 1977 Abood decision of the Supreme Court, which has structured the dues obligations of unionized public employees ever since.

Pamela Harris, who works at home caring for her disabled son, didn’t like those dues obligations, however, and sued to get them overturned. Those dues, however, aren’t all that onerous—for members who decide not to pay for the union’s political activities, they come to 2.5 percent of their pay. That means that if a full-time home-care worker is covered under the SEIU contract, she has seen her yearly pay (assuming 50 weeks of work) rise from $14,500 to (as of December 1) $26,000—a raise of $11,500. She has also seen her yearly union dues go from zero to $650. Not, to any modestly sentient being, a bad deal.

So, Ms. Harris had to pay $650 for her raise? Actually, no. She belongs to a different category of home-care workers, and unlike the workers who voted to join SEIU, her group voted against joining a union. She pays no dues to anybody. Her complaint is that the law would compel such payments if her colleagues had voted to go union—though the law also compels unions to win majority support from workers to represent them at all, which, in her case, the union failed to do. Harris’s apparent concern was that granting home-care workers more pay—something, apparently, that, unlike most home-care workers, she doesn’t need—would raise the state’s Medicaid expenses. The state, and numerous patient advocacy groups, countered that by raising the pay and giving health coverage to those workers, it improves the home-care workforce, reduces turnover, and saves the state money by, first, ensuring more Medicaid patients are able to stay at home rather than go to more costly nursing homes, and, second, by keeping the workers themselves from having to rely on Medicaid for their own medical expenses.

In a five-to-four, party-line decision today, the Supreme Court’s conservative bloc found for Harris. It ruled that home-care workers paid by public funds—and, for that matter, similar employees such as child-care workers—could not be obligated to pay union dues in return for the costs the union incurred for winning them raises and benefits. By law, public-sector unions are required to deliver the same wages and benefits to all the workers in their union, whether they pay dues or not. In essence, the conservatives ruled that workers can be “free-riders”—benefiting from their union’s activities without having to pay a small chunk of their benefit to the union for securing it in the first place.

The decision—written by the Court’s leading union-hater, Justice Samuel A. Alito, Jr.—was a peculiar one, for half of it was devoted to a larger question than that pertaining to home-care workers: whether Abood itself was constitutional. Though he evidently didn’t have enough support to persuade his four right-wing colleagues that every unionized public employee should be free to skip paying dues for the benefits she or he receives, Alito came close to making that case anyway, though he noted at the end of his opinion that, in this case, the ruling only pertained to this “joint employee” category of worker.

If the court had ruled to overturn Abood, it would have overturned four decades of settled law. It also would have crippled the nation’s public employee unions, with huge consequences for the nation’s politics and economy.  Today, the rate of unionization in the public sector is over 30 percent, while it’s only 6.7 percent in the private sector. The reason for this disparity isn’t that postal service workers, say, are liberals while Fed Ex employees are conservatives. It’s that private sector employers routinely oppose their workers’ attempts to unionize, often violating the nation’s labor laws in so doing: the penalties are negligible. Governments in many cities and states (at least, those controlled by liberal or centrist elected officials), by contrast, don’t oppose so emphatically their employees’ attempts to unionize.

If the Court had overturned Abood, unionized public employees would have been free to reap the benefits of contracts without paying for them, which surely, given the economic constraints on the middle class, would seem a rational choice to many. In his decision, Alito proclaimed that unions would undoubtedly be unaffected by enabling workers to ride freely, but, as Justice Elena Kagan pointed out in her dissent (joined by the other three liberals on the Court), many workers would opt for not having to pay and would still reap the rewards. Beyond Kagan’s point, there is also the dollars-and-cents issue of organizing: It costs a lot of money for unions to organize workers and win the right to represent them in the first place, and if they can’t count on dues money coming in once they’ve won that right, the entire enterprise might well be a money-losing proposition for them. In consequence, unions would be inclined to wage fewer such campaigns. And even once they won the right to representation, their clout at the bargaining table would be diminished if more and more of their members opted out of paying dues.

In her dissent, Kagan not only refuted the majority’s argument that the home-care workers weren’t really public employees, she also argued against Alito’s attacks on Abood, and plainly sought to forestall any future Court decision to overturn that ruling. She quoted at length Justice Antonin Scalia’s opinion, in a case from a previous session, essentially upholding the union’s position that employees have no right to receive benefits from unions yet withhold their dues. (Indeed, it may have been Scalia’s conviction on this—which Kagan clearly intended to remind him of —that kept Alito from winning five votes to overturn Abood altogether.) She also repeatedly invoked the principle of stare decisis—that is, the Court’s general practice of adhering to past precedent—pointing out how many subsequent court decisions relied on Abood and how many millions of workers labored under the thousands of contracts that adhere to Abood’s guidelines.

Even without repealing Abood, today’s court decision is plenty catastrophic. It will put financial limits on unions’ campaigns to organize two of the fastest-growing categories of American workers—those who care for the elderly and the sick, and those who care for small children.  It will limit their ability to represent historically underpaid classes of workers, disproportionately female and minority. At a time when the economic prospects of most American workers are unusually bleak, the five conservatives on the Supreme Court have cast their eye on a group of workers who have some of the bleakest prospects of all, and decided to make those prospects bleaker still.