Transnational climate change initiatives have increased in number and relevance within the global climate change regime. Despite being largely welcomed, there are concerns about their ability to deliver ambitious climate action and about their democratic legitimacy. This paper disentangles the nature of both authority and legitimacy of a specific form of transnational networks, transgovernmental networks of subnational governments. It then investigates how a major transgovernmental initiative focusing on tropical forests, the Governors’ Climate and Forests Task Force, attempts to command authority and to build and maintain its legitimacy. The paper illustrates the particular challenges faced by initiatives formed primarily by jurisdictions from the Global South. Three major trade-offs related to authority and legitimacy dimensions are identified: first, the difficulty of balancing the need for increased representation with performance on ambitious climate goals; second, the need to deliver effectiveness while ensuring transparency of governance processes; and third, the limited ability to leverage formal authority of members to deliver climate action in local jurisdictions, while depending on external funds from the Global North.