UPDATE (4/29/2014): In a 6-2 decision today, the U.S. Supreme Court upheld the U.S. Environmental Protection Agency’s (EPA) authority under the Clean Air Act to implement a rule targeting air pollution that crosses state lines.

In the Court’s majority opinion, Justice Ruth Bader Ginsberg wrote,

Air pollution is transient, heedless of state boundaries. Pollutants generated by upwind sources are often transported by air currents, sometimes over hundreds of miles, to downwind states. As the pollution travels out of state, upwind states are relieved of the associated costs. Those costs are borne instead by the downwind states, whose ability to achieve and maintain satisfactory air quality is hampered by the steady stream of infiltrating pollution.

The EPA’s 2011 Cross-State Air Pollution Rule (CSAPR) will require 28 states in the East, Midwest, and South to reduce emissions of sulfur dioxide and nitrogen oxide. The rule is aimed at implementing Section 110 of the Clean Air Act, known as the “good neighbor” provision, which tasks EPA with ensuring that air pollution from one state does not “contribute significantly” to air pollution in other states.

The Natural Resources Defense Council (NRDC) calls the rule “one of the most significant health standards ever adopted by the Environmental Protection Agency.” NRDC's Clean Air Program Director, John Walke, points out, “The EPA safeguards follow the simple principle that giant utility companies shouldn't be allowed to dump their dirty emissions onto residents of downwind states. The Supreme Court wisely upheld this common-sense approach.”

The clean air rule is also a public health standard: it will prevent tens of thousands of premature deaths and illnesses, helping families avoid needless tragedies and resulting in $120 to $280 billion in annual health and environmental benefits. The Supreme Court ruling today is a victory for millions of Americans who will have cleaner air and healthier lives.

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ORIGINAL POST (12/17/2013): On Dec. 10, the U.S. Supreme Court heard arguments over the U.S. Environmental Protection Agency’s (EPA’s) 2011 Cross-State Air Pollution Rule (CSAPR) that would limit power plant emissions of sulfur dioxide (SO₂) and nitrogen oxides (NOx) and would prevent approximately 34,000 premature deaths every year. 

The “good neighbor” provision of the Clean Air Act (known as Section 110) tasks EPA with ensuring that air pollutants drifting from “upwind” states do not “contribute significantly” to air pollution in “downwind” states. EPA directs states to prepare state implementation plans (SIPs), air pollution control “blueprints” that specify how each state will achieve EPA’s national ambient air quality standards (NAAQS) and address air pollution sources that make it difficult for downwind states to meet or maintain the air quality standards. 

In accordance with the “good neighbor provision,” EPA issued the CSAPR rule, requiring 27 eastern states and the District of Columbia to reduce SO₂ and NOx emissions that are capable of crossing state boundaries and making it difficult for downwind states to achieve air quality standards for fine particulate matter and ozone. To achieve these reductions, the rule requires these states to implement a cap-and-trade system.  

EPA first issued a rule to limit cross-state air pollution in 2005 under the direction of the George W. Bush administration. The resulting Clean Air Interstate Rule (CAIR) was challenged by the state of North Carolina and several electric utilities in 2008 before the D.C. Circuit Court of Appeals, which sent the rule back to EPA for revision after finding that CAIR contained multiple flaws.

Yet soon after EPA issued its revised rule, CSAPR, in 2011, it was also challenged by several states, local governments, industry groups, and labor groups. In 2012, the D.C. Circuit vacated the CSAPR rule as exceeding EPA’s authority under the Clean Air Act. The court found that the act did not authorize EPA to require states to reduce emissions by more than their “significant contribution.” The court further concluded that EPA exceeded its authority by failing to provide states an initial opportunity to develop their own state implementation plans to meet the rule’s emissions reduction requirements. The court ultimately invalidated CSAPR and agreed to revert back to the CAIR standard until EPA rewrites the rule. 

On June 24, the Supreme Court granted petitions for review of the D.C. Circuit’s decision filed by EPA and American Lung Association, the Clean Air Council, the Environmental Defense Fund, the Natural Resources Defense Council, and the Sierra Club, and on Dec. 10, the Court heard arguments. Justice Samuel Alito has recused himself from the decision, leaving the case to be decided by the remaining eight justices. For EPA to prevail, at least five of the eight justices must agree to overturn the lower court decision. Such a decision would be a major victory for public health and the environment. According to EPA, in addition to preventing up to 34,000 premature deaths, 15,000 heart attacks, 400,000 cases of aggravated asthma, and 1.8 million missed work or school days would be avoided each year. 

^*Impacts avoided due to improvements in PM2.5 and ozone air quality in 2014

Source: http://www.epa.gov/airtransport/CSAPR/index.html