In 2012 Michigan passed a right-to work statute that lets workers decide whether to join a union and thus pay union dues. The United Auto Workers (UAW), which represents 17,000 state workers, brought a lawsuit claiming the law doesn’t apply to its members because their employment terms are set by the Michigan Civil Service Commission.

Bad call. The Civil Service Commission had long held that, while public employees could opt out of the union, they had to pay union fees. On Wednesday the Supreme Court ruled 4-3 that the commission had no such constitutional authority “to compel civil service employees to make involuntary financial contributions.” Justice Robert Young wrote for the majority that the commission’s rule amounted to a form of taxation, and the power to tax is held exclusively by the legislature. …

Taxpayers should thank the UAW for giving the Justices a chance to return to first legal principles.