Climate change litigation has been hot during the Bush administration-but since 2003, most of the cases have been coming from states and private parties. That year, the Environmental Protection Agency ruled that carbon dioxide is not a pollutant that can be regulated under the federal Clean Air Act. State attorneys general and environmental advocacy groups have tried to use the courts to crack down on greenhouse gas emissions ever since. But the right of states and private parties to use litigation to stand in for the EPA or prompt federal regulation remains un-clear.

“We’re at a watershed in that there is so much interest in litigation associated with climate change, given the vacuum of regulation at the federal level and the fact that the states feel stymied and uncertain as to what authority they have,” says Mark Elliot, an environmental litigation partner at Pillsbury Winthrop Shaw Pittman who successfully represented the Association of American Railroads in a suit to invalidate California state laws regulating air emissions from locomotives. (The case is now on appeal before the U.S. Court of Appeals for the Ninth Circuit.)

Grassroots climate change litigation has come in two forms: States and private parties have either filed statutory claims seeking to force the government to regulate emissions or have brought cases directly against electric utility companies, car manufacturers, and other emitters of green-house gases. The most prominent suit against the government was filed shortly after the EPA’s 2003 ruling, when Massachusetts, joined by 30 other parties, including states, cities, and envi-ronmental groups, petitioned the EPA to define carbon dioxide as a pollutant and regulate its emissions. In April 2007 the U.S. Supreme Court issued a 5-to-4 decision that the EPA has the authority to regulate carbon dioxide and greenhouse gas emissions and ordered the agency to look into appropriate regulation.

The Court’s decision did not, however, set a deadline for EPA action. “The ruling is really just a statement. It’s helpful, but it also highlights the limitations of litigation,” says Massachusetts at-torney general Martha Coakley. “Regardless of what the Supreme Court says, unless we have a change in administration with the appropriate will and ability to address environmental issues, nothing will change.”

On the one-year anniversary of the Supreme Court’s decision, Massachusetts filed a mandamus petition with the D.C. Circuit, requesting that the court require the EPA to move forward with the process of investigating and regulating greenhouse gases. The appeals court denied the peti-tion, but one month later the EPA released its Advanced Notice of Proposed Rulemaking, a document summarizing its work on climate change and asking for public comments. In the preface of the report, EPA administrator Stephen Johnson explained that the Clean Air Act is “ill-suited for the task of regulating global greenhouse gases,” and “would inevitably result in a very complicated, time-consuming and, likely, convoluted set of regulations.”

The EPA is currently considering public comments to the report. “We will continue down that path concerning carbon emissions,” says EPA press secretary Jonathan Shradar.

While the EPA has not yet completed the process of investigating greenhouse gas regulations, emitters of greenhouse gases have not had a break from litigation. Three major cases, none yet decided, have been brought against businesses by states and private parties. In Connecticut v. American Electric Power Company, a coalition of states and the city of New York filed a public nuisance complaint against five electric utilities alleged to be the greatest emitters of greenhouse gases in the United States; in Comer v. Murphy Oil U.S.A., Mississippi property owners who lost homes in Hurricane Katrina claim that greenhouse gas emissions from defendants-several oil, coal, and electric companies-helped create climate change that led to the hurricane; and in California v. General Motors Corp., the state of California filed a public nuisance complaint against six automobile manufacturers, whom plaintiffs allege emit more than 20 percent of carbon dioxide nationwide. The cases have not proceeded very far: The Connecticut plaintiffs are appealing a dismissal at the district court level, the Comer defendants have moved to dismiss a claim amended after an earlier dismissal, and the auto companies have moved to dismiss the California case.

Defendants in these cases have raised the question of whether states and private parties have the power to launch their own enforcement actions, says Joseph Guerra, a partner at Sidley Austin who worked on all three cases and argued Connecticut v. American Electric Power Company in the Second Circuit. “The defendants believe strongly that it’s the role of the political branches of the federal government to address issues such as whether there should be liability and what the standards are,” says Guerra. “It’s their position that it can’t be done on a piecemeal basis by states and private lawsuits.” Courts have so far been favorable to this assessment. When Connecticut v. American Electric Power Company was first dismissed by the U.S. district court in New York, for instance, the court ruled that the matter was nonjusticiable because it involved political questions.

But until there is regulation, there will likely continue to be litigation. Industry attorneys such as Theodore Garrett, cochair of Covington & Burling’s environmental practice group, say that con-tinued reliance on the courts is unlikely to clarify regulation requirements. “Environmental litigation in the past few years, in part spurred by federal deregulatory actions and increased action by environmental groups that have reached the Supreme Court and lower courts, will lead to further litigation in the years ahead,” Garrett says.