We suggest an experimental design for forwarding knowledge on a highly topical and theoretically curious issue: situations where collective action does not voluntary arise and where public attitudes towards third-party attempts to govern individual behaviour therefore come to the fore. The overall aim of the projects is to explore and further understand the interplay between contextual and motivational mechanisms behind public support for governmental behavioral interventions and the implementation of policy instruments. We do so in the context of a high profile, large-scale collective action problem: global climate change. To this end, the project contributes to research on collective action in general, and policy support in particular, in several important ways: First, a country-comparative approach allows us to examine the importance of political context, in particular variations in quality of government, and how it might condition the conclusions fromearlier studies focusing motivational factors on the individual level. Second, we hypothesize that the level of interpersonal, institutional and political trust affects policy support both directly and indirectly, foremost through the perceived effectiveness and fairness of the measure. Third, using web-based survey experiments as our methodological approach allow both for in-depth analyses of causality and interactions, and for explore how levels of support vary between and across different policy measures and packages.