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.