The question of how to overcome the democratic deficits of global forms of governance has led to a pretentious academic debate. To proceed in theory-building, we need to assign systematically the theory-driven assumptions on legitimate forms of governance beyond the nation-state with the various, already observable forms of global governance. Thereto, the paper is aiming at a systematic comparative appraisal of the legitimatory quality of different patterns of governance by applying suitable indicators for their measurement. The innovative potential of this paper is the application of a structured, focused comparison that interconnects a multi-dimensional concept of legitimacy (input-, throughput- and outputdimension) with the triad of international, transnational and private forms of governance. As far as the chosen indicators show a legitimizing effect, they should serve as a standard for upcoming research studies and, by this, contribute to further systematization of studies on global governance. At least, the analysis of the constitutive criteria of cross-border governance arrangements in a legitimacy-based theoretical perspective shall also help to identify their discrete potential for legitimacy and indicate ways for their institutional safeguard and transformation to other arrangements. The conceptual outline will be completed by a case study on forest governance.