The National Highway Transportation Safety Administration (NHTSA) and the U.S. Environmental Protection Agency (EPA) have proposed a new reading of the Energy Policy and Conservation Act of 1975 (EPCA) that governs federal fuel economy standards. The regulations would relax federal greenhouse gas tailpipe standards and fuel economy standards, and preempt emissions standards put in place by California and adopted by other states. This Article examines the agencies’ proposal in light of previous regulatory actions; it considers the agencies’ rationale and finds that their expansive theory of preemption poses significant practical problems and logical flaws. Finally, it examines the agencies’ proposal in light of the U.S. Supreme Court’s preemption jurisprudence, and argues that the agencies’ analysis is lacking because it fails to adequately discuss the objectives of the federal fuel economy laws, nor the purpose and effect of the state requirements.