As renewable energy becomes more cost-effective, there are increasing calls to leave traditional fossil fuel resources “in the ground.” But our ability to do so is constrained both by current technology and by the existing legal and policy structure. This Article examines the improvements in renewable energy technologies and their limitations and economic implications and discusses the challenges facing federal and state attempts to mandate and encourage renewable energy as a result of recent federal court and agency decisions. The author concludes that the main challenge to “leaving it in the ground” is not technological but legal in nature, due to injunctions of proposed federal programs, the states’ loss of regulatory authority from preemption and Commerce Clause rulings, and the uncertainty surrounding federal policy going forward.