The Supreme Court will soon decide whether a state can force government employees to support a union.

In January, the justices heard oral arguments in Harris v. Quinn, a case that could reverse a 37-year-old precedent that greatly empowered government-employee unions at the expense of citizens' constitutional rights.

The Harris plaintiffs are not typical government employees. About 20,000 “personal assistants” in Illinois provide in-home care for disabled individuals eligible for benefits under a federally financed Medicaid program. Under the program, participants can get benefits while living at home instead of in an institution. Hired and fired not by the state but by the patients themselves -- or “customers,” as the program describes them -- the assistants are often family members. They get a check from the state-run Medicaid program but otherwise are “managed” by the customers for whom they care.

This unique arrangement has spared them from having to join — and pay dues to — a government employee union.

In one of his first acts after getting elected governor in 2002, union-backed Rod Blagojevich issued an executive order making Illinois home-care workers into state employees solely for collective bargaining purposes. The Service Employees International Union then “negotiated” a union contract with the state, under which the personal assistants had to support the SEIU through deductions from payments made to them by Medicaid on behalf of their customers. The union collects about $10 million a year in compelled dues and fees from Illinois home-care workers.

Pam Harris, the case's lead plaintiff, cares for her adult son. She and other home-care workers brought a class action against the state, disputing their status as Illinois state government employees and challenging the compelled union payments. They argued that, even if they were government workers, the rules in the public sector should be different from those in the private sector, where compulsory dues and fees have been allowed since the New Deal. Moreover, they claimed, since the SEIU in its bargaining role was influencing government action, the union is really a political organization engaged in lobbying. Compelling government workers to support such organizations violates their First Amendment rights, absent a “compelling state interest” in the outcome. The legal standard applied by the Supreme Court in private-sector cases -- “labor peace” -- is inapplicable when, as in Harris, the unionized employees don't interact in a shared workplace.

The Harris plaintiffs lost in district court and in the Seventh Circuit, but the Supreme Court agreed to hear their appeal. Before the high court, the plaintiffs’ attorneys argued that the ruling in Abood v. Detroit Board of Education (1977) — in which private sector labor law precedents were extended to the public sector for the first time — was wrongly decided and should be reversed. In Abood, a divided court ruled over the dissent of Justice Lewis Powell, who warned that compelled support of public-sector unions violated the constitutional rights of objecting employees.

Absent reform — whether at the judicial or legislative level — the power of government employee unions to influence our politics will only grow. The SEIU and other unions will seek to enroll millions of government-funded service providers. These providers aren’t truly government employees but, like Illinois’s home health-care workers, could be coerced into subsidizing public-sector unions by executive fiat.

The SEIU’s attempts to tie its efforts to private sector collective bargaining are a smokescreen. When the government is the employer, decisions regarding the allocation of taxpayer funds are inherently political.

Judging by the oral arguments in January, the Supreme Court's four liberal justices -- Breyer, Ginsburg, Kagan, and Sotomayor -- support Abood. The four conservatives -- Alito, Kennedy, Roberts, and Thomas -- appeared receptive to overturning Abood. But Antonin Scalia, ever the originalist, seemed skeptical, possibly viewing government-employee unions through the lens of patronage, which the Framers accepted and Scalia has defended elsewhere. One hopes that Scalia reconsiders his position.

The SEIU is practicing peonage, not patronage.

Mark Pulliam is a lawyer and commentator who from 1993 to 2003 covered the California Supreme Court as the legal issues correspondent for California Political Review. This article is adapted from the Manhattan Institute's City Journal, Spring 2014.