Biodiversity continues to decline worldwide, affecting dryland ecosystems that are of significant importance for global biodiversity conservation. Accelerated by climate change, undergoing transformations have been pushing the entire social-ecological system across ecological and social thresholds. Particularly, the decline of pastoral mobility in Mongolia is of great concern, as flexible responses to the dynamic environment are crucial for the sustainability of drylands’ ecosystems. Responding to this concern, Mongolian policymakers design new pasture use and conservation policies. However, the policies might be ineffective in preventing systems from crossing the thresholds, unless policy implementation succeeds in systematically shaping the perceptions of a critical mass of herders and their strategic choices regarding pastoral mobility. We evaluate whether the enacted policies generate the intended consequences. First, we reconstruct the strategic choice and resulting institutions regarding pastoral mobility in the commons domain, where herders jointly use common pastures. Second, we track the process in the political economy domain, where pasture users choose to support or resist policies. Finally, we evaluate the complementarity of the strategic choices and institutions in both domains. In our field research, we employ the “process tracing” method. It relies on observations to trace recurring processes within and between herding communities and incorporates triangulation via various tools, such as expert interviews and focus group discussions. Our findings identify complementarity between the enacted policies and pastoral mobility as individual households comply with the rules and select mobile herding strategies. However, for the complementarity conditions to be held and to create an overall institutional arrangement, a critical mass of herders choosing to comply with the regulations and practice pastoral mobility to reach a social threshold will be crucial