This chapter examines the CITES policy process through the lens of the Advocacy Coalition Framework (ACF), analysing policy changes driven by the beliefs and behaviours of key actors within the policy domain. The examination of this process was carried out by Dutch academicians from the University of Twente, in collaboration with UN researchers. The study focuses on the rejection of WEMS by CITES and its subsequent acceptance by Lusaka Agreement member countries. This chapter highlights the importance of understanding the beliefs and policy processes within CITES over an extended period, a perspective not previously explored in the literature. It demonstrates that ACF serves as an effective framework for unpacking the complexities of the wildlife trade policy subsystem. The analysis reveals how Parties selectively use scientific evidence to support their positions, dismissing it when it contradicts national interests. Drawing on similar studies, it is evident that international organisations must rely on member states and expert evidence to implement policies, particularly in the absence of democratic legitimation. A successful application of ACF requires a comprehensive understanding of both stable and dynamic factors within the policy subsystem, as well as the behavioural patterns of policy brokers during complex decision-making processes. This chapter concludes by underscoring the importance of examining the coalition beliefs in the development of WEMS.