Earlier today, the US Supreme Court issued a ruling in a long-running lawsuit that focused on carbon dioxide's role as a greenhouse gas, which, by some definitions, makes it a pollutant. Just over four years ago, the same court had ruled that the EPA had the duty to determine whether CO 2 qualified as a pollutant under the Clean Air act, a question that the agency subsequently answered in the affirmative. But before that decision had been reached, several states and environmental organizations (along with New York City) had sued several electrical utilities over their emissions. That suit has now been dismissed, as a unanimous Supreme Court has now determined that the Clean Air Act trumps the rights of states to sue.

The targets of the suit were five utilities that together account for about 2.5 percent of the global emissions of greenhouse gasses, so they represent a significant target. The states argued that although there were no laws that applied specifically to carbon dioxide as a pollutant, the Supreme Court in the past had granted standing to these suits under the guise of the federal common law of interstate nuisance. In short, this approach allows courts to set legal standards in the absence of Congressional action for situations where activities in one state cause problems for another. One precedent cited for this is a case where New Jersey sued New York because it was dumping its garbage off the coast.

The case, American Electric Power vs. Connecticut, had initially been dismissed by a judge that held that the suit was focused on a political question; it was reinstated by the Second Circuit's Court of Appeals, which ruled that the states have standing and the issues were not, in fact, political. That case was argued back in 2006, however, and the Supreme Court's decision regarding the EPA's role in carbon dioxide regulation came the following year.

The new decision largely reaffirms that prior decision. If the Clean Air Act applies, then there is a federal statute that governs the issues at hand in this suit—as a result, federal common law cannot apply. The decision, delivered by Justice Ginsburg, notes that it doesn't matter whether the federal law actually results in any practical solution, simply that the law exists. This appears to have been in response to the Court of Appeals decision, which stated, "Until EPA completes the rulemaking process, we cannot speculate as to whether the hypothetical regulation of greenhouse gases under the Clean Air Act would in fact ‘spea[k] directly’ to the ‘particular issue’ raised here."

Still, the opinion makes it clear that the Court thinks the Clean Air Act and EPA action are actually good solutions in this situation. The decision notes that the EPA can be compelled to act via judicial decisions, and any rules it develops are subject to judicial review. Thus, if the states are not satisfied with the EPA's ultimate proposal for regulation, they retain the right to force stricter regulations.

More generally, the ruling serves as a welcome appreciation of expertise. The courts, it notes, simply don't have the expertise that a federal agency like the EPA has access to. "Judges may not commission scientific studies or convene groups of experts for advice," in contrast to the EPA, which "is surely better equipped to do the job than federal judges, who lack the scientific, economic, and technological resources an agency can utilize in coping with issues of this order." Implicit in this is the sense that, when determining whether anthropogenic CO 2 can act as a pollutant and how best to reduce its levels in the atmosphere, the appropriate people to turn to are the ones who know the subject best. In a political environment where expertise is often discounted or disdained, it's a welcome appreciation.

That said, the ruling isn't entirely without its potential problems. The Massachusetts decision did prompt a review of carbon dioxide by the EPA, but that decision was not released until the Bush administration left office. Although the current EPA has issued an endangerment finding, actual regulations aren't expected until next year. The same mechanisms that allow the states to sue if the regulations are too lax will undoubtedly allow many groups to sue because they feel the results are too stringent. It's entirely possible that things will be dragged into the following administration, at which point the regulatory process may end up being restarted. Thus, states are left with little recourse when it comes to compelling action on a time frame that can block a harmful buildup or spread of pollutants.

Finally, two of the Justices who concurred with the general decision (Alito and Thomas) took the time to make it clear that they were not averse to revisiting the Massachusetts decision. "I agree with the Court’s displacement analysis on the assumption (which I make for the sake of argument because no party contends otherwise) that the interpretation of the Clean Air Act adopted by the majority in Massachusetts v. EPA is correct," the two write. Which strongly suggests that, were someone to contend otherwise, they might get a sympathetic hearing. With only two Justices taking that stance, however, it's probably safe to assume that the EPA will remain the ultimate arbiter of how the US deals with its carbon dioxide emissions.