Biobutanol is currently a hot topic within discussions about second-generation biofuels. Its advocates point to the fact that it possesses a higher energy content than traditional bioethanol and, most importantly, that it is compatible with existing fuel distribution infrastructure. While traditional biobutanol production processes have long since suffered from an inability to produce it in an economically viable manner, several recent technological advances have spurred interest from the private sector and several companies are now actively pursuing the commercialization of biobutanol as a transportation fuel. As such, a legal analysis of the regulatory frameworks affecting this commercialization is highly relevant. In this study, we detail and analyze the two most import regulatory frameworks affecting the successful commercialization of biobutanol as a transportation fuel in the United States. First, we provide a thorough description of the US Renewable Fuel Standard (RFS2) and analyze its impact on biobutanol commercialization efforts. Next, we address the US Clean Air Act's so-called ‘substantially similar’ prohibition and detail the three distinct regulatory paths it creates for biobutanol commercialization. Finally, we conclude by exploring ways in which these regulatory frameworks could be altered to mitigate unjustified regulatory burdens. While our study focuses on the commercialization of biobutanol, its regulatory descriptions and analysis are equally informative in regards to the commercialization of other alcohol-based biofuels.