This term at the U.S. Supreme Court seems likely to end with an assault foretold—on America’s public-employee unions. It will come in a case called Janus v. American Federation of State, County, and Municipal Employees, Council 31, which was granted review on September 28. Janus challenges—for the third time in five years—the financial stability of public employee unions. By coincidence, these unions are an important pillar of the Democratic Party.

This is a constitutional dispute conjured more or less out of thin air over the past five years by Justice Samuel Alito.

Janus will be the third attempt since 2012 to gut the unions by court order. Formally it poses a First Amendment question; but under the surface, its central issue is whether public-employee unions are helpful labor organizations or baneful big-government lobbies.

That factual question, as we will see below, will be resolved without any factual record whatsoever. The challengers don’t think facts are relevant—or, perhaps, they regard as relevant only one fact: they think there finally are five votes to attain this long-sought political goal.

The assault foretold began in 2012, with a fairly ordinary labor-law dispute entitled Knox v. Service Employees International Union. To understand Knox and what followed, consider a few details about labor law. Under the National Labor Relations Act, state governments have leeway to structure their relations with their own employees. Some states do not allow their employees to bargain collectively at all; others permit employees to form unions and negotiate, but permit non-members to opt out of the unions altogether; and some—roughly half—permit the employees in a given unit to designate a union as their “exclusive representative,” with authority to negotiate for all the unit’s workers in areas like wages, benefits, working conditions, and on-the-job grievances.

Even in “exclusive representative” states, however, workers can’t be required to join a union. That requirement, the courts have long held, would infringe their First Amendment right of association. However, non-member workers receive the benefits of the union in matters like wages; and thus, in about half of the states, they are required to pay an “agency fee” to the union for those services. This fee is calculated based on a member’s union dues, minus the costs of the union’s “non-chargeable” expenses—overtly ideological activities like political campaigning, legislative lobbying, and litigation for union causes.

In a 1977 case called Abood v. Detroit Board of Education, dissenting Detroit teachers argued that paying an “agency fee” to a public employee union violated their First Amendment free-speech rights, because the funds were used to negotiate with government—an activity that, they said, will always have a political aspect, even when only focused on workplace issues. (Public-employee salaries and pensions, for example, impact overall budget levels; tenure and security rules influence education policy, etc.) Thus, they argued, paying the fees amounted to “compelled speech.”