Rauner, a former private-equity manager who estimates his net worth at half a billion and owns seven luxury homes around the country, despises labor unions and regards workers as overpaid. He wants to allow Illinois cities and counties to declare themselves “right to work” zones. Under Illinois law, corporations and unions can contribute to campaigns; Rauner wants to ban public-employee unions from doing so.

After Rauner’s surprise announcement, Illinois Attorney General Lisa Madigan found that under Illinois law, Rauner lacked the authority to give the order and that withholding the payments violated Illinois law. In another opinion, she pointed out that Rauner’s local “right to work” plan probably also violates federal law. (Under Section 14(b) of the Taft-Hartley Act of 1947, states may pass “right to work” statutes—laws that forbid employers to negotiate exclusive contracts with labor unions; however, the Act does not empower parts of states to do so.)

Rauner filed suit in federal District Court, asserting that the fees are unconstitutional and that he isn’t bound by state law. Madigan intervened on behalf of the State of Illinois: A state official, she argues, can’t ask a federal court to rule on his powers under state law. Late last month, in an attempt to rescue the suit, the governor added three workers as plaintiffs; the court will hear arguments on standing at the end of May. Meanwhile, the unions have filed suit against the governor in state court.

Let’s understand the issue here: Under Supreme Court precedent, states may—if they wish—authorize contracts with public-employee unions designating the union as the “bargaining agent” for employees of different agencies. But under the First Amendment, public workers can’t be compelled to join a union; that would violate their freedom of association. And they can’t be compelled to contribute money to political activities—such as supporting candidates or ballot initiatives, or filing lawsuits against the state. Under a 1977 case called Abood v. Detroit Board of Education, however, states can allow the unions to collect “fair share” fees from objecting workers. These fees pay only for the “non-political” work the union does: negotiating contracts and benefits and administering grievance and other workplace programs. If unions misapply the fees, members can—and often do—sue for a refund.

Union supporters argue that non-members benefit from union-negotiated contracts, and shouldn’t be allowed to “free ride.” In a non-binding part of Harris, however, Justice Alito wrote that everything a public-employee union does is political: “In the public sector, core issues such as wages, pensions, and benefits are important political issues, but that is generally not so in the private sector. ... [A]s state and local expenditures on employee wages and benefits have mushroomed, the importance of the difference between bargaining in the public and private sectors has been driven home.” Thus, he argued, even contract-negotiation fees are “political speech,” for which objectors should not have to pay. His opinion suggests that the Court may soon strike down “fair share” fees (a pending petition for cert. in a California case may give it the opportunity); but it hasn’t done so yet.