Since its establishment in 1967, the Association of Southeast Asian Nations (ASEAN) has expanded its governing issue scope and developed increasingly formalized institutions. At the same time, ASEAN member states have been criticized for their excessive adherence to the norm of strict non-interference in one another’s domestic affairs, thereby hindering further regional integration. This thesis examines the evolution of the non-interference norm within the ASEAN framework, and analyzes how ASEAN elites have practiced and interpreted the norm along with the increasing formalization of its economic regime over time. Through examining ASEAN elites’ discourses, signed agreements and national practices of the ASEAN economic regime, I argue that the non-interference norm has been weakening along with the formalization of the ASEAN economic regime.