Clean Cars Campaign


Briefs in Support of Petitioners

Briefs in Support of Respondents

Other Court Action

U.S. Supreme Court
Tackles Global Warming

On April 2, 2007 the U. S. Supreme Court ruled 5-4 in a strongly-worded opinion that CO2 is a pollutant and that states can regulate its emissions, bolstering California’s Clean Cars Law.

Read the Union of Concerned Scientists fact sheet on implications of the Supreme Court decision.

Background on the Mass. v EPA Suit

The Supreme Court heard arguments on whether carbon dioxide is an air pollutant and on whether the U.S. Environmental Protection Agency can regulate global warming pollution.

The court has based its decision on two questions. First, does the Clean Air Act give the Environmental Protection Agency the authority to regulate greenhouse gases? And second, if it gives EPA that authority, can EPA avoid exercising that authority simply because it doesn’t want to? Clean Cars Campaign members believe the answers are yes, and no, respectively. The Clean Air Act clearly states that carbon dioxide is an air pollutant, and by refusing to regulate it as a pollutant, the Bush administration has evaded the law.

Motor vehicles spew out almost a third of the nation’s greenhouse gas emissions. The world’s leading scientists overwhelmingly agree that greenhouse gases are a major contributor to global warming, and that immediate steps are needed to prevent future damage.

The case before the high court is known as Massachusetts v. EPA, and it stems from 2003, when the U.S. EPA and Bush administration rejected a petition by environmentalists to regulate CO2. The U.S. Court of Appeals for the District of Columbia Circuit upheld the administration position in 2005 in a splintered decision. The U.S. Supreme Court agreed last summer to take the case this session. Massachusetts and 13 other states, along with several cities and various environmental groups including Environmental Defense, the Natural Resources Defense Council, Union of Concerned Scientists, Sierra Club, U.S. Public Interest Research Group and others joined to challenge the administration position.

The decision and its implications are significant for several reasons.

In the absence of federal action on global warming pollution and because of the threat that global warming represents to the economy and environment, California has set its own limits on global warming pollution from cars. Twelve other states have adopted the California standards, and several others are considering adopting them.

The car companies, which have backed the Bush administration in the federal case, have sued to invalidate the California standards. They assert — similar to the Bush administration argument in the federal case — that the state doesn’t have legal authority to limit motor vehicle greenhouse gas emissions.

The Clean Cars Campaign legal argument is simple:

  • Section 302(g) of the Clean Air Act defines an “air pollutant” to include “any chemical, substance or matter emitted into the ambient air.” CO2 and other greenhouse gases clearly meet this definition.
  • Section 202(a)(1) of the Act authorizes EPA to regulate any pollutant emitted by motor vehicles that the agency determines “may reasonably be anticipated to endanger public health or welfare.”
  • In Section 302(h), Congress explicitly defined “welfare” to include “effects on soils, water, crops, vegetation, manmade materials, animals, wildlife, weather, visibility, and climate.” So threats to the “climate” are expressly included in dangers to our “welfare.”
Download the Mass v. EPA Primer.


Briefs in Support of Petitioners

  1. Petitioners' opening brief, filed August 31, 2006

  2. Brief amici curiae of municipalities

  3. Brief amici curiae of climate scientists

  4. Brief amici curiae of Entergy Corporation

  5. Brief amici curiae of Calpine Corporation

  6. Brief amici curiae of Madeleine K. Albright

  7. Brief amici curiae of Tribal governments

  8. Brief amici curiae State of Delaware

  9. Brief amici curiae of religious groups

  10. Brief amici curiae of wildlife conservation organizations and state agencies

  11. Brief amici curiae of the states of Arizona, Iowa, Maryland, Minnesota, and Wisconsin

  12. Brief amicus curiae of Aspen Skiing Company

  13. Brief amici curiae of regional environmental groups

  14. Brief amici curiae of former EPA Administrators

  15. Brief amici curiae of ocean and conservation organizations

  16. Petitioners reply to U.S. government and industry respondents, filed November 15, 2006

Briefs in Support of Respondents

  1. Respondents' opening brief

  2. Brief amici curiae–Competitive Enterprise Institute

  3. Brief amici curiae from Michigan and other states

  4. Brief amici curiae from Robert Bork et. al.

  5. Brief amici curiae from Ken Starr