The U.S. Supreme Court  heard oral arguments Feb. 24 in a significant environmental case in which the justices appeared to be split on whether the Environmental Protection Agency had the authority to develop greenhouse gas regulations for powerplants, refineries, and other “stationary sources.”

The justices did not appear willing to revisit the court's 2007 Massachusetts v. EPA decision, which said that EPA could regulate greenhouse gases if the agency found that they endangered public health.

Instead, the case before the court on Feb. 24 centers on a narrower question of whether EPA has the authority to use two provisions to regulate greenhouse gases emitted by “stationary sources.”

The case may have a minimal impact on the construction industry. It focuses on two provisions of the Clean Air Act under which carbon dioxide and other greenhouse gases are regulated as “air pollutants.” It leaves other provisions of the law intact.

The first contested provision involves a program to prevent local air quality from deteriorating; the other is a recordkeeping program for stationary-source operating permits.

Attorneys for the American Chemistry Council, the U.S. Chamber of Commerce, the state of Texas, and the Utility Air Regulatory Group said that the air-quality program was not intended to regulate global substances like carbon dioxide.

But the U.S. Solicitor General, Donald Verrilli, argued that that interpretation represented “a clear misunderstanding” of the air-quality program. He said that other diffuse substances like ozone, which can still have a local impact, have been regulated under the air-quality program for years.

Justices Sonia Sotomayor and Elena Kagan said that existing law gives agencies significant latitude in making reasonable interpretations of ambiguous statutory language.

Sotomayor told Peter Keisler, arguing for the industry groups, “If your side can’t even come to one interpretation [of the Clean Air Act], why shouldn’t we defer to the Agency?”

The conservative wing of the court questioned why EPA had developed a threshold that exempts smaller facilities from the requirements of the program to avoid an “absurd” result. Justice Antonin Scalia asked Verrilli, “Aren’t you compelled where there is ambiguity to adopt the interpretation of the statute that does not produce absurdity rather than adopting the interpretation that produces absurdity and then going around altering the provisions of the….statute?