In aligning with the growing body literature on the debate whether R2P has been accepted or implemented in Southeast Asia, this article explores how ASEAN member states problematise R2P. The responses of ASEAN countries to mass atrocities in the region indicates neither the case of ‘R2P in practice’ nor the implementation (without adoption) of the R2P. Rather, it suggests subsidiary behaviour in the sense that the countries have used normative principles such as state sovereignty, non-interference and self-determination to offer normative resistance to international interference especially when the R2P norm is taken into account, and to justify their limited and incremental response to the mass atrocities. It has been emphasised that ASEAN already has set principles and approaches to address the issues and therefore, there is no urgency to use R2P to respond the cases and adopt the norm into ASEAN.