In their talk, Per-Olof Busch and Helge Jörgens explore and elaborate a simple idea: governments coordinate their policies not only through multilateral cooperation or coercion, but also through decentralized processes of cross-national policy diffusion. Policy diffusion occurs when governments voluntarily and unilaterally adjust their domestic policies to the previous policy choices of other jurisdictions by imitating or learning from these. They show theoretically and empirically that diffusion is an influencable mode of international policy coordination and that it may result in a substantial degree of international policy coordination. clusters of countries that have adopted similar institutions, laws, policies, instruments, and regulations, in the field of environmental protection. Per-Olof Busch and Helge Jörgens develop their argument against the empirical background of a specific type of international political order: clusters of countries that have adopted similar institutions, laws, policies, instruments, and regulations, in the field of environmental protection.