Southeast Asia is home to many diverse cultures across and within national borders. The vast majority of these borders evolved out of those created during the colonial period in the region. While the Westphalian state system was imposed in the region, the post-independence period has illustrated traditional understandings of sovereignty are rhetorically prevalent in Southeast Asia. This is noticeable in the 1976 Treaty of Amity and Cooperation, which was a founding document of the Association of Southeast Asian Nations (ASEAN). This treaty bound its signatories not to interfere in another’s domestic affairs yet there remain several high profile interventions which have trumped the noninterference norm – what explains this? Examples range from the 1975 Indonesian invasion of East Timor to the 1978 Vietnamese invasion of Cambodia, and to a more contemporary example of ASEAN member states’ participation in United Nations peace operations in East Timor from the early 2000s onwards.