While the federal government has been slow to address problems such as climate change, many states have adopted innovative approaches to address the climate impact of using natural resources to produce energy, including aggressive approaches to regulating carbon emissions and renewable and clean energy standards. This Article identifies an emerging challenge that subnational regulation faces in the energy and environmental context -- what I will call “maladaptive†federalism -- and argues that federalism discussions need to account for its possibility. Part I highlights adaptive regulation as a form of federalism, echoing a vision for subnational regulation many federalism scholars and policymakers have endorsed over the past two decade...