Meta-organizations are crucial devices to tackle grand challenges. Yet, by bringing together different organizations, with potentially diverging views on these grand challenges, meta-organizations need to cope with the emergence of contradictory underlying social orders. Do contradictory orders affect meta-organizations’ ability to govern grand challenges and if so, how? This article investigates these essential questions by focusing on the evolution and intermeshing of social orders within international governance meta-organizations. Focusing on the International Whaling Commission and the grand challenge of whale conservation, we show how over time incompatible social orders between the meta-organization and its members emerge, evolve and clash. As our study shows, this clash of social orders ultimately removes the ‘decidability’ of certain social orders at the meta-organizational level. We define decidability as the possibility for actors to reach collective decisions about changing an existing social order that falls under a collective’s mandate. We argue that maintaining decidability is a key condition for grand challenges’ governance success while the emergence of ‘non-decidability’ of controversial social orders can lead to substantial failure. We contribute to both the emerging literature on grand challenges and organization theory.