Supreme Court to Hear Challenge to Rules on Mercury From Power Plants

The Supreme Court agreed Tuesday to hear a major challenge to the limits set by the Obama administration on emissions of mercury and other toxic pollutants from coal-fired power plants.

It is the latest effort by industry groups to roll back regulations that would reduce emissions like mercury, soot, sulfur, smog and carbon dioxide. The case also threatens to undermine one of the administration’s most significant victories and chip away at President Obama’s legacy.

John Walke, a lawyer with the Natural Resources Defense Council, called the regulation of mercury emissions that are at issue in the new case “the greatest clean air achievement of the Obama administration’s first term.”

The industry groups say the Environmental Protection Agency is overstepping its authority under the Clean Air Act by issuing the series of regulations. Republicans have attacked the rules as a “war on coal” and an example of what they say is the executive branch’s overreach.

The basic question in the new case is whether and when the E.P.A. must take regulation costs into account. The agency’s interpretation is that the Clean Air Act, which requires regulations to be “appropriate and necessary,” does not demand that costs be taken into consideration early in the regulatory process.

In the Supreme Court term that ended in June, the justices heard cases filed by industry groups against two of the Obama administration’s environmental regulations — one aimed at limiting power plant pollution that wafts across state lines, the other at cutting planet-warming greenhouse gas emissions.

The E.P.A. won the first case and largely prevailed in the second, though the Supreme Court indicated that it remained prepared to impose limits on the agency’s regulatory authority.

The case against the mercury pollution rule is likely to be followed by more fights. The E.P.A. on Wednesday will release a regulation to cut ozone pollution. Next year, the agency is scheduled to finalize rules that would slash greenhouse gas emissions from power plants. Environmental law experts say the Supreme Court’s decision in the mercury case may provide some hints about how those other rules might fare.

“Is this part of a larger trend of the Supreme Court exerting greater authority over E.P.A.’s regulations?” asked Roger R. Martella Jr., a general counsel at the agency during President George W. Bush’s administration. The new case is a challenge by more than 20 states, along with industry groups and energy companies.

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