Policy makers frequently learn from the policy experiences of other governments. Lessons inform decision making, diffusing policy across borders. Using interviews with key policy actors and a comparative analysis of United States and European policy contexts, this study identifies and describes causal mechanisms through which newly emerging offshore wind energy policies diffused across governmental borders. In so doing, this article demonstrates a new approach to understanding policy learning and diffusion to complement the large‐N, quantitative analyses that form the bedrock of the literature. The findings support the argument that future studies must account for policy diffusion between subnational and foreign national governments, as well as diffusion between coequal administrative agencies in different policy subsystems—“directions” of diffusion that are invisible to traditional methods, yet likely to become increasingly common in the face of climate change and other wicked problems.

Objective This article investigates how different types of policies (morality based and highly technical) inform early‐stage policy learning and diffusion processes. Methods Using process tracing, interviews, archival research, and cross‐case analysis, this article describes and compares the emergence of medical marijuana and offshore wind energy policies in U.S. states. Using iterative data collection and analysis, the study identifies which factors proffered by the literature affect the policy learning and diffusion process. Results Despite representing different types of policies, there were significant similarities across both cases: State actors drew lessons from Europe; policy lessons from Europe were weaponized by national political interests in an effort to stymy state‐level diffusion; and, as policies diffused to other states, organized opposition curtailed. Conclusion This study demonstrates how the stage of diffusion can be as determinative of the policy learning context as the type of policy, and highlights how the diffusion and typology literatures can inform each other.