Regional intergovernmental organizations and macropolitical boundary work.

The article examines how regional intergovernmental organizations (RIOs) such as the European Union (EU) and the Association of Southeast Asian Nations (ASEAN) construct and reshape their macropolitical boundaries—formal, politically significant demarcations between member and non-member states—and how these boundaries influence regional conflicts. It develops a three-dimensional framework of macropolitical boundary forms based on malleability (flexibility of boundary location), stratification (hierarchical division between members and non-members), and modality (bilateral or multilateral relations). Through case studies of the EU's role in the Cyprus conflict and ASEAN's management of South China Sea disputes, the article argues that hierarchical but malleable boundaries can enable conflict amelioration, while fixed and stratified boundaries risk aggravating tensions. It concludes with policy recommendations urging RIOs to structure boundaries to balance these dimensions, such as promoting multilateral engagement when enlargement is unlikely, to better manage conflicts between member and non-member states.