This article provides an explanation for the adoption and partial abandonment of subnational regional greenhouse gas emissions trading systems on the United States’ East and West Coasts as well as the country's Midwest by focusing on gubernatorial entrepreneurship. The analysis is twofold: On the one hand, the article explores the motivations of governors to act as entrepreneurs, pushing for the adoption of the policy innovation ‘greenhouse gas emissions trading systems’. On the other, it examines the interaction between contextual factors and gubernatorial entrepreneurship, arguing that this can explain the adoption and abandonment of subnational regional greenhouse gas emissions trading systems. The analysis suggests that strong gubernatorial entrepreneurs can seize windows of opportunity for ambitious climate policy that are opened by a federal-state context in which the federal government is inactive, creating a regulatory void. In doing so, they take a risk due to the uncertainty of whether the policy will be (politically) successful. Since politicians often are risk averse, trying to avoid blame for policy failure, such proactive gubernatorial entrepreneurship requires strong motivations. With the increasing likelihood of imminent federal policy, additional governors can become active but their entrepreneurship tends to be weaker since they react to a different window of opportunity in which they take a lower risk than the strong gubernatorial entrepreneurs. Also their motivations tend to differ from those of the proactive gubernatorial entrepreneurs.