Does the public legitimacy of International Organizations (IOs) depend on their institutional settings? In this paper, we seek to provide an answer to these questions by focusing on the authority dimension of an IO’s institutional design. We argue that changes to scope of IO authority on two different sub-dimensions employ effects on the IO’s public legitimacy: the bindingness of policy decision and the majority/voting rules in the IO’s governing body. More specifically, we hypothesize that the direction of effects varies between citizens with higher and lower levels of cosmopolitanism – somewhere else aptly described as, “Anywheres” and “Somewheres”. While the cosmopolitan-minded Anywheres should prefer higher levels of IO authority, the communitarian-minded Somewheres should be more favorable towards lower authority levels. We test our expectations by conducting a self-administered factorial survey experiments in six different countries. The empirical results support our arguments and imply that the effectiveness of IO reforms in regard to public legitimacy might feed into the cosmopolitan-communitarian societal cleavage.