The U.S. Supreme Court heard oral arguments this week in the Massachusetts v. EPA suit. To many environmental groups and outdoor businesses that depend on snowfall, this is considered a landmark global warming case. Petitioners in this case are asking the Court to determine that the Clean Air Act authorizes the Environmental Protection Agency to regulate carbon dioxide and other greenhouse gases as air pollutants. The EPA claims it has no such authority, while the petitioners claim that it does, and must, by law use this authority to reduce CO2 emissions.

The original petitioner in the case was Massachusetts, but several other state and local governments have signed on as well, including California, Connecticut, Illinois, Maine, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, and Washington.

Environmental groups and outdoor businesses that have connections to the case include Environmental Advocates, Environmental Defense, Friends of the Earth, Greenpeace, Natural Resources Defense Council, Sierra Club, and the Aspen Skiing Company.

The High Court’s decision is likely to have a far-reaching impact on future action to fight global warming at both the state and federal levels. “Since CO2 is the main culprit behind global warming, something which undoubtedly will negatively affect both our weather and climate, it seems quite clear that the plain language of the statute grants EPA this authority,” said Sierra Club Senior Attorney David Bookbinder. “It’s not every day that a group of states comes to the Supreme Court begging it to grant a federal agency more authority. That alone should demonstrate the magnitude of this problem and the need for action by the federal government.”

According to reports from the floor of the Supreme Court, Justices Scalia and Alito have been showing signs of ruling against Massachusetts, while Breyer and Kennedy indicated a potential decision against the EPA. All other justices were difficult to read one way or the other based on their questions.

This case is likely to have a direct bearing on the eleven states that have adopted global warming emissions standards. Under the Clean Air Act, California can set its own motor vehicle standards, and other states can choose California or federal standards.

“Either way the Court rules, support is building in Congress for new legislation to curb global warming,” added NRDC’s David Doniger. “In the meantime, we are making every possible effort to get the Bush administration to follow the laws we have today, and to start cutting global warming pollution without further delay.”