The Supreme Court appeared split Monday during oral arguments challenging the authority of an Obama administration program to regulate greenhouse gas emissions from factories and power plants.
The high court decision, expected this spring, is poised to spark renewed debate of the politically charged topic ahead of the November mid-term elections.
Several lawsuits, bundled together into one case, oppose an Environmental Protection Agency program that requires large industrial sources to obtain Clean Air Act permits for their greenhouse gas emissions, which is blamed for global warming. The rule applies to new facilities and existing ones that have been expanded or modified.
The ruling isn't expected to threaten the agency's overall ability to regulate greenhouse gases, as other regulatory tools could be used.
But the challenge provides the high court an opportunity to clarify the agency's authority. A ruling favorable to the EPA could be viewed as validation for the administration's approach, while a decision against the agency would give welcome fodder to the administration's anti-regulation critics.
The court's liberal-leaning justices seemed satisfied that the administration -- through the EPA -- has the legal authority to impose specific regulations aimed at curbing greenhouse gases.
And Justice Sonia Sotomayor suggested she was troubled by the plaintiffs' varied arguments and interpretations related to which pollutants the EPA can and cannot regulate.
"If your side can't even come to one interpretation, why shouldn't we defer to the agency?" she asked Peter Keisler, an attorney representing the American Chemistry Council, which is among two dozen manufacturing and industry groups challenging the rule.
Keisler responded that "the deference that an agency is afforded is always going to be limited to reasonable interpretations."
The administration says its rules are necessary because the 50-year-old Clear Air Act didn't specifically address greenhouse gases when it was written and because climate change "is an urgent environmental problem."
"There really is an urgency here," Solicitor General Donald Verrilli Jr. warned the court. "It is the gravest environmental problem that we face now as far as [the] EPA and EPA's judgment, and it is one that gets worse with the passage of time."
The Supreme Court ruled in 2007 that the agency has the authority under the Clean Air Act to limit emissions of greenhouse gases from vehicles. The administration has used the ruling as justification to expand its regulatory authority to stationary facilities such as factories and power plants.But conservative-leaning Justice Antonin Scalia suggested that such a move was government overreach and a legal stretch.
"Why would it be unreasonable to give EPA authority to regulate mobile sources and not authority to regulate stationary sources?" he said. "That doesn't seem to me irrational at all."
Keisler added that "while other programs of the Clean Air Act give EPA authority to regulate greenhouse gases from stationary sources, [the administration's program] does not."
The utility industry, the U.S. Chamber of Commerce and 13 states led by Texas are asking the court to rule that the EPA overstepped its authority by trying to regulate greenhouse gas emissions through the permitting program.
Energy & Environment Writer Zack Colman and the Associated Press contributed to this article.