Specifically, all unionized government employees — other than first-responders and law enforcement officers — would have to opt in to have unions withdraw dues from their paychecks.

In his decision, Walsh said the law, known as House Bill 1413, would gut the state’s constitutionally guaranteed collective bargaining rules.

“In sum, a system like HB 1413 — in which very few conditions of employment are subject to meaningful bargaining, and the few conditions over which the parties can negotiate may be unilaterally abrogated by management — does not even give an illusion of collective bargaining,” he wrote.

Republicans have fought hard for the law. A similar version was approved three years ago, but former Gov. Jay Nixon, a Democrat, vetoed it.

The sponsor of the legislation, Rep. Jered Taylor, R-Nixa, said he was reviewing the ruling and couldn’t say yet if lawmakers would try to fix the problem before they adjourn in mid-May. “I’d say we’re more in a holding pattern right now,” Taylor said.

In a statement, Lori Sammelmann, an employee of the Ferguson-Florissant School District, said the law hurts rank-and-file government workers.