On April 2, in Massachusetts v. Environmental Protection Agency, the U.S. Supreme Court ruled that the Environmental Protection Agency (EPA) currently possesses the authority to regulate greenhouse gas emissions under the Clean Air Act and that it cannot evade its statutory responsibility to exercise that authority. The majority opinion written by Associate Justice John Paul Stevens resolved the issue of whether the EPA has authority to regulate greenhouse gas emissions. On account of that decision, the political and economic landscape has moved farther away from the scientific debate in a direction toward laying a framework for stemming greenhouse gas emissions.

In reaching the decision that the Clean Air Act authorized the EPA to regulate greenhouse gas emissions, the Supreme Court highlighted the Clean Air Act’s expansive language. It noted that the Clean Air Act declares, “The Administrator shall by regulation prescribe (and from time to time revise) in accordance with the provisions of this section, standards applicable to the emission of any air pollutant from any class or classes of new motor vehicles or new motor vehicle engines, which in his judgment cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare…”

Furthermore, when it comes to greenhouse gases, the Court found no evidence of Congressional understanding that there was something sacrosanct about greenhouse gases that they should be exempted from air pollution regulation. Instead, such gases fit the the Clean Air Act’s definition of an “air pollutant.” That Act defines an “air pollutant” as “any air pollution agent or combination of such agents, including any physical, chemical, biological, radioactive…substance or matter which is emitted into or otherwise enters the ambient air.” The sweeping nature of the language strongly suggests that it was Congress’s intent at that time to give the EPA sufficient authority to respond to existing and new air pollution issues that could arise in the future.

Air pollutants that impacted property, animals, weather, and climate were all subject to the EPA’s regulatory authority. In fact, the Clean Air Act defined the public “welfare” to include, among other things, “effects on…weather…and climate.” As such, if one adopted a strict constructionist view that the Supreme Court should interpret laws based on the original intent of the Congress at the time those laws were drafted, one would have no choice but to conclude that Congress intended that the EPA have wide-ranging authority to regulate air pollutants, including greenhouse gases, and that such regulation could seek to mitigate weather or climate impacts.

In explaining the EPA’s authority concerning greenhouse gas emissions, the Supreme Court shot down the EPA’s fairly recent claim that, in its view, it lacked such authority. The Court illuminated the fairly recent origins of the EPA’s position. In doing so, it referenced an April 1998 memo written by Jonathan Z. Cannon, then EPA General Counsel that affirmed that the EPA understood that it possessed such authority as distinct from its decision at the time to refrain from exercising that authority. Cannon wrote, “While CO2, as an air pollutant, is within EPA’s scope of authority to regulate, the Administrator has not yet determined that CO2 meets the criteria for regulation under one or more provisions of the Act. Specific regulatory criteria under various provisions of the Act could be met if the Administrator determined under one or more of the provisions that CO2 emissions are reasonably anticipated to cause or contribute to adverse effects on public health, welfare, or the environment.” That view was reaffirmed by his successor, Gary S. Guzy, in testimony before the House Energy and Environment Subcommittee in October 1999. At no time subsequent to the testimony did Congress adopt legislation—binding or non-binding—that attempted to restrict or rescind the authority Cannon and Guzy described. This inaction on the part of Congress provided additional support that it was the intent of Congress at the time to give the EPA sufficiently broad authority that included the regulation of greenhouse gas emissions.

Afterward, the Supreme Court ruled against the EPA’s failure to regulate greenhouse gas emissions. In the years since the Clean Air Act was enacted and especially in the past 20 years, scientific understanding of climate change and the role greenhouse gases play in driving climate change, has advanced markedly. In 1990, the Intergovernmental Panel on Climate Change (IPCC) stated that “emissions resulting from human activities are substantially increasing the atmospheric concentrations of…greenhouse gases [which] will enhance the greenhouse effect, resulting on average in an additional warming of the Earth’s surface.” In 1995, the IPCC reaffirmed this earlier finding while cautioning, “Our ability to quantify the human influence on global climate is currently limited because the expected signal is still emerging from the noise of natural variability, and because there are uncertainties in key factors.” In February 2007, the IPCC concluded that there is at least a 90% certainty that human emissions of greenhouse gases have been driving the ongoing climate change.

As the scientific consensus was solidifying, Europe and various States, including California and Massachusetts, were becoming increasingly concerned about the issue. In contrast, the EPA maintained a course that could reasonably be described as “regulatory indifference.” The combination of growing public concern over climate change, the observed effects of climate change, and the EPA’s regulatory indifference, sparked litigation that culminated in the Supreme Court’s decision. With Massachusetts arguing that the EPA’s failure to regulate greenhouse gas emissions was contributing to the injury inflicted on its coastal areas from a rising sea-level, the Supreme Court ordered that the EPA comply with its obligation under the Clean Air Act to begin regulating greenhouse gas emissions. At the same time, the Court narrowed the EPA’s discretion to avoid such action, declaring, “Under the clear terms of the Clean Air Act, EPA can avoid taking further action only if it determines that greenhouse gases do not contribute to climate change or if it provides some reasonable explanation as to why it cannot or will not exercise its discretion to determine whether they do… If the scientific uncertainty is so profound that it precludes EPA from making a reasoned judgment as to whether greenhouse gases contribute to global warming EPA must say so. That EPA would prefer not to regulate greenhouse gases because of some residual uncertainty…is irrelevant. The statutory question is whether sufficient information exists to make an endangerment finding.”

In sum, the Supreme Court unambiguously declared that the EPA has statutory authority to regulate greenhouse gases. It then ordered the EPA to use that authority to begin the process, while imposing a formidable hurdle against the EPA’s continuing to avoid such regulation. This precedent will likely lead to broad changes in America’s regulatory framework over time. However, it likely will not lead to an economic “massacre” that some critics have predicted in the wake of the Supreme Court’s opinion. In fact, the Supreme Court explicitly addressed the concern over unreasonable regulation in adding, “EPA would only regulate emissions, and even then, it would have to delay any action ‘to permit the development and application of the requisite technology, giving appropriate consideration to the cost of compliance.’” As a consequence, especially given the strong scientific consensus on the issue, the Supreme Court has now cleared the way for the political environment to begin regulating greenhouse gas emissions.