The most important fact about Monday’s oral argument before the U.S. Supreme Court in Friedrichs v. California Teachers Association is that this case—one of the most important of the term—will be decided on the basis of no facts at all.

The petitioners in Friedrichs are asking the Court to hobble unions that represent more than 9 million public employees in 23 states and the District of Columbia. That decision will have large consequences for those employees, for the states that employ them, and for the political system. But the Court will decide the case without, apparently, serious consideration of those effects.

Representing the challengers, the conservative lawyer Michael Carvin described a public-employee union as a purely political group that “advocates an ideological viewpoint” his clients “do not approve of.” Every single thing a public-employee union does, he said, is a matter of public concern; contract negotiations with teachers’ unions, for example, affect class size, teacher promotion policies, and overall state funding—every one of them a hotly contested political issue. In contrast, the union lawyer David Frederick told the Court that many of the union’s activities are “mundane matters” without political content.

Will ending the fees cripple or destroy public-employee unions? Who knows? Will unions become less effective in making labor-management relations harmonious? Who knows? Search the joint appendix in this case—nearly 700 pages of pleadings, docket entries, and opinions—and you won’t encounter even one piece of live testimony from union leaders or state officials. The record contains no testimony or studies by labor economists.

That’s because the challengers below—represented by the anti-union Center for Individual Rights—demanded that the lower courts rule against them on a bare record. Current Supreme Court precedent is flatly against them, and lower courts can’t overturn Supreme Court decisions. We want to hurry this case up to the high court, the challengers said; don’t slow us down with facts.

Now they have the case where they wanted it, they ooze confidence—because in the past four years, the conservative majority has twice signaled that it is tired of public-employee unions and wants a chance to radically rewrite the law in this area.

There are public-employee unions in all 50 states and the District, of course. But in the jurisdictions that Friedrichs would affect, the legislatures have opted for something called the “fair-share” or “agency fee” system. Under this system, a majority of public employees in a given “bargaining unit”—the school system, say, or the police agencies—can vote to designate a union as their “exclusive bargaining agent.” That union then must represent all the workers in the bargaining unit. Since public employees cannot be forced to join a union, that will include a number of non-members.

But representation takes time and money. Under existing law, unions cannot charge non-members with their share of costs for activity that qualifies as political; but they can require a fee for the “chargeable” expenses of representation—money spent, union lawyer Frederick told the Court, for such things as “research, legal representation, conferring and consulting, communicating with members, trying to ascertain what the positions of all the workforce are before the union presents a policy.” Under a 1977 case called Abood v. Detroit Board of Education, those charges are permitted to prevent non-members from “free riding”—gaining the benefits of representation without paying for them.

Abood admitted that imposing the fees “has an impact upon their First Amendment interests.” But as an employer, government can limit employee speech rights to some extent; in the case of the “agency shop,” the Court reasoned, “such interference as exists is constitutionally justified by the legislative assessment of the important contribution of the union shop to the system of labor relations established by Congress.”

That is, federal law allows states to choose agency agreements—and those that have done so justify that choice in practical terms. Good relations with the employees, the argument goes, depends on mechanisms by which their concerns can be heard. Many states had seen strikes by teachers and other public workers—including crucial ones like correctional officers, garbage workers, teachers, and police. Agency agreements, the states argue, allow the two sides to negotiate and agree without open conflict.

In a 2014 case called Harris v. Quinn, however, the five-justice conservative majority unloaded with fury on “agency fee” agreements. That case concerned an agency agreement in a “bargaining unit” of Medicaid-funded home-health workers. Writing for the five conservatives, Justice Samuel Alito spent 12 full pages trashing Abood: That case, he suggested, underestimated the burden of “agency fees” on dissenting employees and overestimated the importance of unions for “labor peace.” The opinion then retreated from the brink, holding that the home health workers were not “full-fledged” state employees anyway, and thus not covered by Abood. The hint was broad: bring us the right case and we will stake this puppy for good and all.

Which brings us to the dispiriting argument Monday. The central point made by the challengers is that the very idea of “chargeable” expenses is a fraud: Any word uttered by a public-employee union is big-government, collectivist ideological propaganda. Chief Justice John Roberts asked California Solicitor General Edward Dumont for an example of a collective-bargaining issue that “does not present a public policy question.” Dumont gamely mentioned “mileage reimbursement rates” and “public safety.”

Wrong, said the chief justice. “That's money. That's how much money is going to have to be paid to the teachers...And the amount of money that’s going to be allocated to public education...that’s always a public-policy issue.”

Later, Justice Sonia Sotomayor offered another suggestion. “The unions in California do teacher training,” she said. Carvin, remarkably, would not concede that even practicing fire drills was anything but sneaky union politics. “They do safety training,” he said of the union. “Can you think of something that’s more a matter of public concern, that’s more of an ideological point, that’s more important?”

The state, the union, the United States, and a number of state governments argued to the Court that history and experience had convinced 23 states that having an effective union was an important tool in managing the workplace. So what? the conservatives effectively replied. The state hadn’t shown that the union would collapse without fees. Would it be less effective? Who knows? Anyway, the states may claim to want effective union negotiating partners, but trust us, they really don’t. “They don’t want them to be effective,” Carvin assured the justices, “because nobody wants a strong bargaining partner that’s going to drive up public expenditures.”

In general, the majority displayed all the knowledge and sophistication—and not as much of the curiosity—that one would expect from random callers to a drive-time radio talk show. That’s the problem with the Court’s brave new First Amendment world. The Court—or at least its conservative majority—will decide the fate of America’s public-employee unions in the same airless, fact-free plane of abstractions it visits when it decides campaign-finance cases.

Overruling Abood will be a major step, and the critics have not demonstrated any special reason for scrapping the precedent except that they don’t like it. “You start overruling things,” Justice Stephen Breyer asked Carvin, “what happens to the country thinking of us as a kind of stability in a world that is tough because it changes a lot?”

I couldn’t count five justices who want to stay with “stability” however. The most likely outcome is a sharply divided 5-4 opinion upending the world of public-employee unions. Less likely is a decision that unions may continue charging fees, but can’t require objectors to “opt out.” Under this modified system, workers would have to fill out an “opt-in” form agreeing to the charges. That result would be no more strongly moored in precedent, and would likely weaken unions—though no one can say how much because, again, there’s no factual record in this case.

In the ever-expanding blob that is the conservative majority’s new model of the First Amendment, facts, consequences, and effects really don’t matter.

Or perhaps they matter all too much. Cynics will point out that Friedrichs—like the campaign-finance cases—is aimed at tilting the political playing board in favor of conservative interests. In the new world of Citizens United, the First Amendment allows corporations to use shareholder funds to campaign for individual candidates; under the proposed Friedrichs rule, it would at the same time forbid public employees to use worker funds even to sponsor safety training.

That blow to public-employee unions, however inconsistent it may be legally, will seem all too horribly consistent in another way.