It’s been a difficult June for President Obama’s allies in organized labor. First, Wisconsin Gov. Scott Walker easily beat back a union-funded recall election, ensuring the survival of his reforms to collective bargaining and other public-sector union privileges. In Virginia, the bureaucrats controlling the nation’s largest ongoing public works project — the Silver Line to Washington Dulles International Airport — were forced by political pressure to drop union contracting preferences that had threatened to exclude firms from Virginia, a right-to-work state.

And then this week, organized labor received yet another blow in the form of the Supreme Court decision Knox v. SEIU. The 7-2 ruling blocks public employee unions from padding their political coffers with contributions from unwilling non-members. It applies to closed-shop states, such as California, where the government deducts union representation fees even from the paychecks of nonmembers. . . . Labor unions provide a service to their members — a service that is worth whatever those members are willing to pay, but not a cent more. The Supreme Court’s ruling affirms this valuation. It continues a welcome trend across America of plugging up and sealing off unfair revenue streams that public-sector unions, over the years, have managed to extract from the unwilling — from taxpayers, governments and nonmembers.

The money machine seems to be breaking down.