The localization of the Sustainable Development Goals (SDGs) is widely promoted as a strategy to align global development objectives with local priorities through decentralization and participatory governance. However, empirical evidence on how localization reshapes governance relations in regions with strong commons-based institutions remains limited. This paper examines the implementation of SDG localization in Arunachal Pradesh, India, focusing on high-altitude grassland commons managed by the Monpa pastoral community in Tawang district. Building on fieldwork and systematic analysis of policy documents and development schemes, the analysis examines how SDG targets are translated into subnational planning frameworks and how these processes interact with customary commons governance institutions. The findings show that SDG localization through centrally designed programs, politics of ambiguity and standardized indicators make limited provisions for recognizing or integrating indigenous governance institutions. As a result, pastoral commons and associated livelihood systems remain largely peripheral to SDG-aligned planning, despite their direct relevance to sustainability outcomes. This mode of localization reproduces centralized decision-making authority and frames sustainability as a technical and administrative exercise rather than a context- specific governance process marginalizing rather than reinforcing existing systems of collective resource management. It highlights the need to assess SDG localization not only through universal performance indicators but through its effects on governance structures, knowledge systems, and long-standing socio-ecological relations in indigenous and frontier regions.