The first section of this article focuses upon how Realism has emphasized the impact of material factors like balance of power in explaining the limitations of ASEAN's role in shaping the regional order in south-east Asia. The second section highlights how the Constructivist scholars have stressed on the behavioural and procedural norms of ASEAN as the primary determinants in explaining the behaviour of member states. The section explains the uniqueness of the ASEAN norms as the basis for the emergence of a collective identity among the ASEAN member states. The third section provides an analysis of three different case studies in order to explain whether ASEAN's position on these issues was motivated by the Realist premise of power balancing considerations, or the Constructivist perspective of shared norms and identity of actors. These case studies include ASEAN's response in the aftermath of the Kampuchean crisis of 1978-79, the territorial disputes between the People's Republic of China and some of the ASEAN states in the South China Sea and the expansion of ASEAN membership. The final section evaluates the extent to which ASEAN norms have remained significant in explaining its regional role in south-east Asia. It argues that security concerns of ASEAN states are often products of the interplay of ideas, norms, interests and power balancing considerations.