In 2003, the EPA said that because green house gasses were not air pollutants, they had no power to set emission standards for vehicles under the Clean Air Act. Later that year several states and environmental agencies brought suit against the EPA. The suit progressed through the DC circuit and despite challenges brought by the EPA, finally made it to the Supreme Court.

In their 5-4 decision, the court did not say the EPA should step up and regulate vehicle CO2 emissions, but did clearly state the agency had authority to do so. While this decision marks the first time climate change has reached the Supreme Court, they avoided taking any position on the issue making sure to stay neutral on the matter.

Vehicle emissions are a major contributor to global warming, but can be some of the toughest to regulate through conventional policy routes. This will probably not be the last we hear about the legal battles surrounding vehicle emissions as auto manufacturers will more than likely fight any regulations the EPA may come up with.

To raise awareness of the decision and to put a little pressure on the EPA, activist group Environmental Action began an online, grassroots outreach campaign to get people to send a message to encourage the EPA to act.

Further reading:
The New York Times; Massachusettes Attorney General's Office, Environmental Defense