In this action, the U.S. Environmental Protection Agency (EPA) is rescinding the Administrator's 2009 findings of contribution and endangerment and repealing all greenhouse gas (GHG) emission standards for light-duty, medium-duty, and heavy-duty vehicles and engines to effectuate the best reading of Clean Air Act (CAA) section 202(a)(1). The EPA determines that CAA section 202(a)(1) does not authorize the Agency to prescribe emission standards in response to global climate change concerns for multiple reasons, including the best reading of the statutory terms "air pollution," "cause," "contribute," and "reasonably be anticipated to endanger." This statutory interpretation is corroborated by application of the major questions doctrine. The EPA further determines that GHG emission standards for new motor vehicles and engines do not impact in any material way the public health and welfare concerns identified in the Administrator's prior findings in 2009. On these multiple and independent bases, the EPA concludes that it lacks statutory authority to regulate GHG emissions in response to global climate change concerns under CAA section 202(a)(1), and is not finalizing the additional bases for repeal set out in the proposed rule.