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SCOTT JAGOW: Tomorrow, the Supreme Court takes up one of the biggest environmental cases in years: Massachusetts v. EPA. Thirteen states and several groups want to force the Environmental Protection Agency to regulate carbon dioxide. That of course is the main culprit in global warming. The plaintiffs claim the EPA has the authority to regulate CO2 under the Clean Air Act. The EPA says it doesn't. And Corporate America is divided on who it wants to win this case. Sarah Gardner reports from our Sustainability Desk.

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SARAH GARDNER: When Entergy filed a friend of the court brief in Massachusetts v. EPA, it noted that the case "makes for strange bedfellows."

That's because the New Orleans-based electric company finds itself siding with folks like the Sierra Club and native Alaskan tribes. Entergy is among a handful of utilities that favor regulation of carbon dioxide emissions.

BRENT DORSEY: We have about 20 percent of our generation from coal-fired plants.

Although those plants would be penalized in a carbon-regulated country, Entergy's Brent Dorsey says the vast majority of his company's electricity comes from natural gas, which doesn't emit as much carbon ,and nuclear, which gives off none at all.

Many utilities more reliant on coal adamantly oppose regulation. Still others are conflicted, but want a decision either way.

Climate change consultant Mark Trexler:

MARK TREXLER: We have hundreds of power plants on the drawing boards right now in the United States. We have more than 90 coal plants on the drawing boards, and a lot of these executives just wish they had some clue where this issue was headed.

More united in their opposition are auto makers and dealers. They don't want the EPA in charge of fuel economy standards and warn carbon regulation will raise vehicle prices and limit consumer choice.

Gloria Berquist is with the Alliance of Auto Manufacturers.

GLORIA BERQUIST: So anything that puts us at cross purposes with consumers is challenging.

If car companies feel threatened by carbon regulation, then others feel vulnerable without it. The Aspen Skiing Company filed a friend of the court brief in Massachusetts v. EPA. The resort argued that warmer temperatures = less snow = melting profits.

Aspen's Auden Schendler:

AUDEN SCHENDLER: Now the ski industry is saying, hey, we could be out of business by 2050 or definitely by 2100 if we don't do something.

Other companies haven't weighed in on the Supreme Court case but have told Congress they favor restrictions on carbon. Wal-Mart, Shell and GE are among them.

Regulation critic Marlo Lewis says GE has plenty of bottom line reasons to favor caps on CO2. The company's invested heavily in carbon-free energy, and it's a leading producer in technology to capture emissions from coal plants.

MARLO LEWIS: So this would give them a government-protected market for a technology which is currently not economic for utilities to invest in.

If the Supreme Court rules in the EPA's favor and decides that agency has no authority to regulate greenhouse gases, advocates of carbon regulation will put more pressure on Congress to do it. Few politicians look forward to taking the heat for that vote.

I'm Sarah Gardner for Marketplace.