Governance, from local to global levels, relies increasingly on private governance arrangements. Private actors, specifically corporations and civil society organizations, increasingly design, implement and monitor rules and standards that guide and prescribe behavior in a range of policy areas, including sustainability, banking and international security, to name a few. Even though the involvement of private actors in global politics is not a new phenomenon, the creation of cooperative arrangements in the form of organizations that lead to private regulation - thus complementing traditional ways of political influence - is relatively novel. This paper focuses on private rule-setting organizations that have emerged in the global governance of sustainability. It starts from the observation that, despite seemingly performing similar roles and functions, organizations differ both in terms of outputs they produce as well as rules of participation and decision-making. Accordingly, the paper evaluates whether organizations providing a more inclusive and participatory approach in relation to others have different implications for the quality and relevance of rules (outputs). Hence, it aims to shed light on the way private rules and standards are decided and the associated implications, in view of their increasing role and relevance in sustainability governance. In more detail, we contend that there is no linear relation between democratic legitimacy and effectiveness. While inclusiveness and representativeness in the standard-setting process will probably lead to more stringent and comprehensive rules, those regulatory systems with high stringency will be the ones least taken up. Empirically, the paper illustrates its argument with a comparison of five private rule-setting organizations that have emerged in the global governance of fisheries sustainability: the Marine Stewardship Council, Friend of the Sea, the Aquaculture Stewardship Council, the Global Aquaculture Alliance and GlobalGAP. © 2013 Copyright ICCR Foundation.