Diffusion research often characterizes the role of the federal government in innovation adoption as a supportive one, either increasing the likelihood of adoption or its speed. We examine the adoption of medical marijuana laws (MMLs) from 1996 to 2014 to shed light on what motivates states to adopt innovations that are in explicit defiance of federal law. Furthermore, we examine whether federal signals have any influence on the likelihood of adoption. In doing so, we utilize implementation theory to expand our understanding of how the federal government's position impacts state policy innovation adoption. We find mixed evidence for the influence of federal signals on the adoption of MMLs. The results suggest that medical marijuana policies are much more likely to be adopted in states when proponents have the political or institutional capital, rather than a medical or fiscal need. Moreover, this political capital is sufficient independent of the federal government's real or perceived position.