Upholding EPA Regulation of Greenhouse Gases: The Precautionary Principle Redux

Abstract

The debate over the precautionary principle versus cost-benefit analysis in environmental decision making has engaged legal and policy experts for decades. At its heart, the precautionary principle counsels that governmental action should be taken to reduce the risk of serious harms, even if the evidence defining the harm is not sufficient to meet the evidentiary standard of certainty in a civil proceeding, and even if uncertainty is too great to be able to quantify and compare costs and benefits with precision. In Coalition for Responsible Regulation v. EPA, the U.S. Court of Appeals for the District of Columbia Circuit upheld EPA’s regulation of greenhouse gas emissions from motor vehicles on the ground that such emissions endanger public health and welfare. Both EPA and the court placed primary reliance on the precautionary principle of the Clean Air Act’s endangerment standard as construed in the 1976 D.C. Circuit case Ethyl Corp. v. EPA, upholding EPA’s regulation of another motor vehicle pollutant, lead emissions resulting from the use of lead additives in gasoline. This Article contends that the issues and outcomes of the two regulatory decisions demonstrate why a precautionary approach— balancing probability and severity of harm and acting before full quantification of benefits and costs is possible—is a necessary framework for sound decision making on the most complex and consequential threats to the environment, including the extraordinary challenge of climate change.