The U.S. Supreme Court on Monday rejected federal regulations curbing mercury emissions and other harmful pollutants from power plants.
The 5-4 ruling, which split the high court's conservative and liberal justices, said that the Environmental Protection Agency didn't initially account for the costs of the regulations on businesses. The federal Clean Air Act requires “appropriate and necessary” measures to regulate emissions; the court majority determined that regulators did not meet that threshold.
"One would not say that it is even rational, never mind 'appropriate,' to impose billions of dollars in economic costs in return for a few dollars in health or environmental benefits," said Justice Antonin Scalia, who wrote the decision.
The EPA first took steps to curb emissions from power plants in 2000, then resumed work on the rules in 2009 after the end of the Bush administration.
The rules, which were finalized in 2012 and set to fully take effect next year, aimed to cut emissions of mercury, arsenic, cadmium, chromium, nickel and others from coal-fired and oil-fired plants by about 90 percent.
The agency cited a slew of potential medical problems stemming from those emissions and up to $90 billion in potential public health benefits.
Industry groups and 21 states led by Republicans, however, challenged the rules in federal court. Their attorneys argued that although the EPA considered the health costs, regulators did not factor compliance costs into the agency’s decision to move forward.
The EPA later determined that removing the pollutants would cost plant operators about $9.6 billion annually.
The American Coalition for Clean Coal Electricity called the ruling "a win for American consumers and a rebuke of EPA’s callous approach to regulations."
"When EPA rewrites this regulation, we can only hope it uses real costs and benefit figures rather than those pulled out of its magic bag of tricks," said Mike Duncan, the group's president.
The federal appeals court in Washington, D.C. previously upheld the rules, but the high court reversed that decision on Monday. The case will be returned to lower courts to address the cost issue.
Justice Elena Kagan, who wrote the dissenting opinion, said the ruling deprived the EPA "of the latitude Congress gave it to design an emissions-setting process sensibly accounting for costs and benefits alike."