In his state-of-the-state speech last week, the newly elected Republican governor of Illinois, Bruce Rauner, called on his state’s local governments to pass right-to-work ordinances to improve their economic competitiveness — aware, presumably, that there is no way the deep-blue Illinois legislature is going to approve such a law across the state.

But he’s got more tricks up his sleeve to improve the state’s dire economic and budget picture, including a daring one he uncorked yesterday: He issued an executive order declaring, based on the logic of a 2014 Supreme Court case, that state employees who don’t want to join a union don’t have to pay anything to the union that represents them.

The move, preventing the state from compelling the payment of so-called “fair-share fees,” could help marginalize the unions that have put the state in such dire budgetary straits — and weaken public unions in a number of other deep-blue states, too.

About 6,500 Illinois state workers currently pay such a fee, also known as an agency fee, which is generally close to or the same as actual union dues. It allows one to register opposition to the union while still holding a union job, but you can’t vote in elections, etc.; in the relevant unions, if you do that, you’re still obligated to pay anywhere from 79 percent to 100 percent of full union dues.

A decent share of Illinois’s public workers already opt out of union membership — 6,500 of them out of the 42,000 or so who are under union contracts. But Rauner’s decision, if it’s upheld, should make the number of union dissenters grow substantially, because it would allow them to pay neither union dues nor a fair-share fee, saving them big money if they leave the union.

As Manhattan Institute fellow Dan DiSalvo puts it to me, “when agency or fair-share fees are not permitted, as is the case in the right-to-work states and now Wisconsin, the membership rolls and revenues collected by the unions tends to fall. When workers can opt out, a healthy slice of them do.” This, naturally, weakens the unions’ ability to bargain with state government.

Rauner immediately filed a preemptive legal case opposing the likely union pushback, so the legal debate can begin in earnest. If he wins or a California case under similar logic wins at the Supreme Court, he’s won an important victory for Illinois and other states, quite legally, without even going through the legislature. If he fails, it’s definitely a loss for conservative legal efforts to weaken unions’ special privileges.

For now, as the case works its way through the legal system, state workers under union contacts in Illinois will have to keep paying dues or fair-share fees, and fair-share fees will be kept in escrow. (The money, not accessible to the union, either, isn’t a gigantic amount but may hurt them a bit.)

His legal argument is that the logic of 2014’s Harris v. Quinn Supreme Court decision, which prevented the state from requiring union dues or fees from quasi-state workers — in that case, people paid by Medicaid to take care of their disabled family members — should also apply to state workers in general.

Why? Because such a policy violates even full-time state workers’ First Amendment rights, on two grounds: that, while union members have the legal “Hudson” right to get back dues specifically spent on political purposes, such funding is fungible so they’re being forced into political contributions anyway, and, more important, that public-sector collective bargaining is an inherently political process.

Unions say that fair-share fees just pay for the costs of negotiating contracts and representing employees, but the Rauner administration argues in its complaint, noting especially Illinois’s dire financial straits:

When Unions expend dollars collected pursuant to the Fair Share Contact Provisions to lobby or bargain against reductions to their own benefits packages or to shift more significant reductions to other state programs or services, there is no principled distinction between the Unions and the various special interest groups who must expend money on political activities to protect their own favored programs and services.

A state law that forces state workers to contribute to that kind of political activity, Rauner argues, violates the First Amendment.

And that’s why he can, if he’s right, do this via executive order: The Illinois constitution prohibits the enforcement of laws that violate the U.S. Constitution, and Rauner says, after a deep legal review, he thinks the fair-share fees are unconstitutional forced expression. (They were ruled constitutional by the Supreme Court in a 1977 case.)

This is a more daring maneuver on labor law than Rauner would probably have ever tried legislatively. Reformers in other liberal, union-heavy states such as Pennsylvania have instead tried more gradual steps, like passing legislation to prevent the state from gathering union dues itself, forcing the union to pay for the administrative costs instead.

There’s some real debate over whether the logic of the Harris v. Quinn decision can be extended to regular state workers — last year, some members of the court appeared willing to take the logic pretty far, calling unions’ special privileges into question, but it just isn’t clear. We may have an answer to the question before Rauner gets it, because a similar case is just one step away from the nation’s highest court.

Teachers in California alleging collective bargaining is an inherently political act they can’t be forced to support have already filed for the Supreme Court to grant their case, and it could be heard as early as October 2015. If they triumph, in Friederichs v. California Teachers Association, it will presumably prevent all the states around the country — around 20 — that currently require union dues or fair-share fees from doing so in the future. For now, Rauner’s Illinois is in limbo — and, duly elected, he deserves credit for putting them one step closer to breaking the tyranny of public-sector unions.