The US government defended its regulation of greenhouse gas emissions from power plants before the Supreme Court on Monday, after coming under attack from industry and Republicans alike.
The top court is not expected to rule until June on the policy, which requires new power plants, factories and other stationary industrial sites to use the latest energy-efficient technologies.
Republicans and energy interests argue that the rules, which have been adopted by the Environmental Protection Agency, are bad for the economy and possibly illegal.
But President Barack Obama's administration says the changes are necessary to combat global warming and are a centerpiece of US efforts to reduce air pollution.
"This is an urgent environmental problem and this is one that gets worse with time," argued Donald Verrilli, a lawyer for the Obama administration.
Michigan and Texas have joined 10 other states and numerous industry groups to call on the high court to strike down some of the rules put in place by the EPA, which calls for lowering the carbon emissions of the highest polluting factories.
Frustrated by inaction in Congress, the EPA adopted regulations in 2010 to limit carbon emissions by stationary facilities, such as power plants, and by motor vehicles.
In two prior cases, the Supreme Court has held that the EPA could regulate emissions from motor vehicles and power plants and other stationary sources under the 1970 Clean Air Act, even though at the time, greenhouse gases were not well understood and were not explicitly placed under EPA authority.
One of the parties opposing the rules, the National Association of Manufacturers (NAM), said the EPA has stepped beyond the bounds of its authority.
"Manufacturers have long argued that the EPA's greenhouse gas regulations for stationary sources are some of the most costly, complex and harmful they have ever faced," the group said in a statement after the more than 90-minute-long session.
Inside the courtroom, the justices appeared reluctant to change their 2007 decision to grant the EPA, a federal agency, power to limit greenhouse gas emissions.
"We are bound both by the result and the reasoning of the Massachusetts v. EPA case," said Justice Anthony Kennedy, who is likely the swing vote between four conservative justices who oppose the EPA rules and the four liberals who appear to support them.
"There's no need to reverse Massachusetts," argued Jonathan Mitchell, a lawyer representing the state of Texas.
Lawyer Peter Keisler, representing NAM, said at issue is the EPA's stated intent "to rewrite the threshold" of allowable emissions.
According to the Constitutional Accountability Center's president Doug Kendall, the arguments by states and industry appeared weak.
"The attempt of industry to frame this case as a power grab by EPA fell flat today before the Supreme Court," he said in a statement.
"Justices across the ideological spectrum rejected the notion that they could walk away from the seminal case they decided just seven years ago, which held that EPA has the authority to regulate global warming, the defining environmental challenge of our time."
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