Editors' Summary: On July 15, 2005, the U.S. Court of Appeals for the D.C. Circuit upheld EPA's decision not to regulate carbon dioxide and other greenhouse gas (GHG) emissions from automobiles, thereby thwarting efforts to use the CAA to curb climate change. In this Article, Zachary Tyler analyzes the court's decision, arguing that the court should have reached the opposite conclusion. Tyler looks at the events that led to the dispute, including how the Clinton and Bush Administrations differed in their interpretation of the CAA with respect to GHGs. He also examines the majority, concurring, and dissenting opinions and their differing views on standing, the CAA, and policy considerations. He concludes that while the court left certain issues unresolved, their ruling is a clear setback in efforts to curb climate change.