The Environmental Protection Agency is imbued with significant authority to limit climate pollutants, according to the United States Supreme Court, but it must remain vigilant against political pressure lest we lose our best defense against the growing levels of greenhouse gas emissions. Earlier today the United States Supreme Court reaffirmed its 2007 ruling that the Environmental Protection Agency (EPA) has the authority to regulate greenhouse gases (GHGs) that cause global climate change. Unlike the 2007 decision in Massachusetts v. EPA, however, today’s decision does have a downside. The Court also determined that because EPA has the authority to control GHGs, a lawsuit against major carbon emitters, which asked a federal court to establish GHG emission limits, cannot proceed. While the immediate outcome of this case is disappointing, it highlights and affirms the broad authority that EPA has to slow global climate change, it sends a warning to certain politicians that gutting EPA’s authority could backfire–in the form of more, not less regulation–and it should serve as a reminder that advocates for action on climate change must continue to provide support for EPA’s ongoing rulemakings. Today’s ruling comes from a lawsuit filed in 2004. At that time, eight states, New York City, and several private, not-for-profit land trusts sued the five largest carbon dioxide emitters in the country: American Electric Power, Southern Company, Xcel Energy, Cingergy Corporation and the Tennessee Valley Authority. The plaintiffs argued that these five polluters collectively emitted 650 million tons of carbon dioxide annually, accounting for 2.5 percent of all human emissions or 25% of emissions from the electric power sector. In their lawsuit, the plaintiffs urged that federal “common law” provided them with protection from the harms associated with climate change, for example, rising sea levels, increased risk of severe weather events, and human health threats. “Common law” is the law that is not written into statutes and constitutions, but is slowly developed over the course of time, tracing civil customs through court decision. Based on this source of law, the plaintiffs argued that the court should fashion specific carbon emission limits to stop the power companies from contributing to climate change.

The Supreme Court today ruled that the states, New York City and the land trusts could not bring their lawsuit under the federal common law because Congress empowered EPA to take responsibility for regulating climate change. To use the legal terminology, the Court decided that any arguments under the common law are “displaced” by the Clean Air Act, which gives EPA authority to regulate GHGs and limit climate change.

The obvious downside of this ruling is that the plaintiffs lost their case, meaning that one tool for slowing climate change–federal common law–is no longer available. But this decision also has far reaching positive implications. During the administration of President George W. Bush, EPA argued that it did not have authority to regulate GHGs. In 2007 the Supreme Court ruled that EPA did have authority to regulate GHGs. That ruling was controversial to some, including justices on the Supreme Court. There was a very real possibility that in today’s ruling, the Court would undermine EPA’s authority. Instead, the ruling strongly and explicitly supported EPA’s legal mandate to limit GHGs. In fact, in unanimous agreement, the Supreme Court explained that EPA’s authority to regulate GHGs is the reason that the common law argument fails. The unanimity of this logic is important because in 2007 four justices (Alito, Roberts, Scalia and Thomas) all disagreed, saying that EPA did not have authority to regulate GHGs. In today’s ruling the same justices concurred that common law was not a valid tool specifically because Congress empowered EPA, rather than courts, to take the lead in GHG regulation. Justices Alito and Thomas made a special note in which they said that they were not necessarily agreeing that EPA has authority to regulate GHGs, but since none of the parties to the case argued otherwise, they would accept EPA authority only for the sake of argument. Notably, Chief Justice Roberts and Justice Scalia did not qualify their opinions in the same way, suggesting that they now agree with EPA’s authority. Regardless of the opinions of each justice individually, this case directly and strongly supports EPA’s authority over GHGs and reaffirms the 2007 case of Massachusetts v. EPA.

The fact that the Supreme Court relied exclusively on EPA authority means that if members of Congress succeed in their attempts to de-fund or de-authorize EPA’s efforts to slow climate change, then these anti-EPA officials may find that they have hurt their position more than they have helped it. Critics would like to prohibit EPA from carrying out the suite of climate safeguards that EPA is currently developing. Ironically, if these critics succeed in their efforts, then the basis of today’s Court ruling fades. If Congress removes EPA’s GHG authority, then EPA rules will no longer displace the federal common law and courts may be authorized to issue their own rulings. Utilities and anti-EPA members of Congress must prefer consistent rules coming from EPA than disparate and unpredictable rules coming individually out of different courts across the county. Utilities like certainty. The degree of certainty that EPA provides is much higher than the patent uncertainty that utilities would face if EPA lost its authority and courts took on the responsibility to protect individuals from a changing climate. And make no mistake about it, as the impacts of a changing climate grow it will be impossible for courts to legally abstain from filling the void that would open if EPA could not address greenhouse gas pollution.

Perhaps the most important implication of today’s ruling in American Electric Power v. Connecticut is not that EPA has authority, or even that the utilities would be best served by supporting said authority, but that EPA is the single most important battleground in the effort to achieve significant GHG reductions and slow the changing climate. We have seen that Congress does not have the political will to take on climate change, and the courts are not fully equipped or permitted. Only EPA is clearly authorized and sufficiently expert. EPA has proposed a number of rules that would help slow GHG emissions, from the Best Available Control Technology “Tailoring Rule” to the New Source Performance Standards for new and existing power plants. These rules are a start, but they are not a solution. There must be strong support for the rules that exist and will soon be proposed, but there must also be continued pressure on EPA to progress beyond these early steps. EPA, like Congress, is subject to political whims and political pressure. For instance, EPA recently announced that it would delay until September the New Source Performance Standards that should be proposed in July. Not only must we remain dedicated to helping EPA develop strong and protective rules, we must also remain focused on reminding EPA that these rules cannot wait. If nothing else, the United States Supreme Court has sharpened this focus and highlighted that at least for now EPA is the best hope for combating climate change.