Massachusetts et al. v Environmental Protection Agency et al., 549 U. S. 497 (2007).

Twelve states, along with a number of cities and private organizations filed suit against the EPA for determining that it lacked authority to regulate carbon dioxide under the Clean Air Act. On appeal to the Supreme Court, respondents, which included the EPA and ten other states, argued that petitioner lacked standing and that the EPA properly determined that it lacked jurisdiction to regulate carbon dioxide. The Supreme Court held that petitioner had standing, noting first that this was not the typical case “between two private parties.” Rather, the case involved injury to Massachusetts in its capacity as a quasi-sovereign. In particular, the EPA’s failure to regulate carbon dioxide contributed to rising sea levels, which caused erosion to Massachusetts’ coastline. Because states, as quasi-sovereigns, possessed interests beyond that of their citizens in the environment within its jurisdiction, Massachusetts had standing. The Court then concluded that the EPA possessed authority pursuant to the Clean Air Act to regulate carbon dioxide.

State of Connecticut et al. v. American Electric Power Company, Inc. et al., 564 U.S. 410 (2011).

Eight states, New York City and three land conservation groups sued AEP, three additional electric power companies and the Tennessee Valley Authority arguing that the power company’s greenhouse gas emissions levels constituted a public nuisance because they contributed to climate change. Before the Supreme Court, AEP argued that the Clean Air Act displaced state common law causes of action. The Supreme Court held that pursuant to the Clean Air Act, the EPA was the dominant regulator of emissions, and the Act displaced the common law of nuisance.  After Massachusetts, the EPA took steps to regulate emissions from light-duty trucks, other vehicles, and power plants.  Based on these actions as well as the statutory provisions, the Court concluded that the Act evinced an intent to preempt common law claims.


EPA et al. v. EME Homer City Generation LP et al., 134 S. Ct. 1584 (2014).

Fourteen states, as well as a number of municipalities and energy industry groups, sued the EPA, arguing that the agency exceeded its authority when it created the Cross-State Air Pollution Rule (Transport Rule), which limits nitrogen oxide and sulfur dioxide emissions from upwind states whose emissions pollute the environment of downwind states.  Pursuant to this rule, each state was allocated an emissions budget.  At the same time this rule was created, the EPA also promulgated federal implementation plans (FIPs) for each state because it had previously determined the state implementation plans (SIP) were inadequate.  The states argued that the EPA could not issue federal implementation plans until the states had first been given the chance to develop a new SIP to comply with the emission budgets.  The industry groups also argued that the EPA unreasonably interpreted the Clean Air Act by prohibiting only amounts of emissions that “contribute significantly” to the pollution in downwind states.  The EPA, and nine states that intervened in support of the agency, argued that the rule was valid.

The Supreme Court rejected both arguments, holding that the Clean Air Act did not require the EPA to give states a second chance to file SIPs before implementing an FIP.  The Court also held that the EPA’s method of calculating and then determining emissions budgets was reasonable.

Utility Air Regulatory Group et al. v. EPA et al., 134 S. Ct. 2427 (2014).

Thirteen states and a number of industry groups challenged several of the EPA’s actions.  First, the plaintiffs challenged the agency’s “Endangerment Finding,” in which the EPA determined that greenhouse gases may “reasonably be anticipated to endanger public health or welfare.”  Second, the plaintiffs challenged EPA’s “Tailpipe Rule,” which sets emission standards for certain classes of motor vehicles.  Third, the plaintiffs challenged EPA’s “Timing and Tailoring Rules,” which regulated greenhouse gas emissions from stationary sources such as power plants and refineries pursuant to Title V of the Act.  Soon after the case was filed with the D.C. Circuit, fifteen states moved to intervene in support of the EPA.

The Supreme Court, drawing on Massachusetts v. EPA, upheld the agency’s “Endangerment Finding,” and the “Tailpipe Rule.”  However, it warned that the agency cannot apply the broad definition for “air pollutant” as was the case in Massachusetts to all provisions of the Clean Air Act, particularly with respect to regulation of stationary sources under Title V since the agency itself has routinely given it a narrower meaning.  The Court then stated that the agency must limit its approach under the “Timing and Tailoring Rules” to facilities that are already required to obtain permits.


Michigan, et. al., v. EPA et. al., 135 S. Ct. 2699 (2015).

The Supreme Court found that the EPA exceeded its authority by failing to consider costs to regulated parties when making threshold determinations on whether to regulate hazardous air pollutants from power plants under 42 U.S.C. §7412(n)(1) of the Clean Air Act.  Writing for a 5-4 majority, Justice Antonin Scalia wrote that even under the Chevron deferential standard “EPA strayed far beyond those bounds when it read [42 U.S.C.] §7412(n)(1) to mean that it could ignore cost when deciding whether to regulate power plants.”

In her dissent, Justice Elena Kagan – joined by Justices Ginsburg, Breyer and Sotomayor – described the majority’s conclusion as a “peculiarly blinkered way for a court to assess the lawfulness of an agency’s rulemaking” since EPA did take costs into account “at multiple stages and through multiple means as it set emissions limits for power plants.”  Furthermore the EPA’s decision not to consider costs at the outset of the regulatory process was well within the agency's province, “given that it would do so in every round thereafter—and given that the emissions limits finally issued would depend crucially on those accountings. Indeed, EPA could not have measured costs at the process’s initial stage with any accuracy.”