The Supreme Court awarded the National Mining Association (NMA) a 5-4 decision granting our request to strike down the Environmental Protection Agency’s (EPA) 2012 standard for mercury and other emissions. The court held that the EPA was unreasonable in not considering costs — including the cost of compliance — before deciding whether further regulations on power plants were appropriate and necessary.

In other words, EPA didn’t use common sense when deciding it was “appropriate” to impose a rule whose costs far outweighed its benefits. “Appropriate” is a commonplace word to help guide common sense decisions. We’re not parsing Heidegger’s “Being and Time” here or conjugating Old Norse verbs. In setting this plain criterion under this section of the Clean Air Act, Congress assumed regulators, whatever their political views, were essentially rational people bound by broadly acceptable standards of conduct and judgment, people who, if given your dog to walk around the block, would return home with the same animal.

Five justices decided this EPA can’t be trusted to exercise common sense, so they might withhold the customary discretion the court gives to regulators.

But this administration makes such a belief seem naïve, almost quaint. Lawmakers did not anticipate this breed, much less that the nation’s energy grid would one day be transformed by doctrinaire fanatics running an environmental agency that is indifferent to cost, to the law, to congress and to public opinion. That sounds like the old Soviet Politburo, not the U.S. government.

Yet, fast forward to today, and we see how environmental mullahs at the EPA thought it was entirely appropriate to expect Americans to pay $1,600 for $1 in benefits. A rule that triggered the closure of 60 GW of affordable power generation, not the 6 GW that the EPA estimated. A rule that led to many of the 45,000 coal jobs lost since the rule was imposed in 2012 and that stranded hundreds of millions of dollars spent on clean technology.

Luckily, five of the nine justices agreed with us that such a rule fails the common sense test. The words of Justice Scalia in the majority opinion should be inscribed over the portals of the EPA’s headquarters: “It is not rational, never mind ‘appropriate,’ to impose billions of dollars in economic costs in return for a few dollars in health benefits.”

The practical impact of the decision on the number of power plants spared retirement remains to be seen. Many plants have already made the decision to retrofit or retire. But more than 400 coal units representing 142,000 MW of capacity have been granted one-year extensions for compliance. Some portion of this capacity will live another day to strengthen coal demand and the electricity grid.

Also unclear, if more important at this point, is the ruling’s impact on the EPA’s coming carbon reduction rule, the so-called Clean Power Plan, expected later this summer. Forget any possibility that the EPA would amend its proposal in light of the Supreme Court’s mercury rule. EPA Administrator McCarthy struck a defiant tone at a House committee hearing, dismissing NMA’s victory as “very narrow” and irrelevant to the Clean Power Plan.

We’ll see about that. Five justices decided this EPA can’t be trusted to exercise common sense, so they might withhold the customary discretion the court gives to regulators. The court also decided the EPA can’t simply “rebake” the law by accepting words that favor its regulatory ambition while ignoring words that restrain it. In the Clean Power Plan, the agency ignores all precedent by straying far from the fence line of a power plant, where it has standard-setting authority, to the entire grid, where it doesn’t.

Mike Tyson said, “everybody’s got a plan until they get hit in the mouth.” The EPA just got hit in the mouth, and its plan may need revision.

Luke Popovich is a spokesperson for the National Mining Association, the industry’s trade group based in Washington, D.C.