Policy diffusion studies often infer that learning occurs, but statistical analyses cannot demonstrate it definitively. The spread of medical marijuana offers the opportunity to take a closer look at whether policy and political learning occur during diffusion. An increasing number of states have adopted medical marijuana policies in defiance of federal prohibition and in the space created by federal inactivity. Furthermore, early adopting states have adapted their programs to account for changes in the industry and to coincide with recreational marijuana programs. This article sheds light on how the laws have evolved over time due to policy learning, political learning, and local adaptation. Specifically, we review how states have incorporated best practices from others (policy learning) and how the laws have been repackaged in more politically conservative states (political learning).