Regional organizations are a type of international organizations with limited or selective membership. As a result, scholars tend to study regional organizations as ‘clubs’. Theorizing regional organizations as clubs, however, obscures an important aspect of their evolution. How do we account for the effects of resource sharing and enlargement when an organization becomes less exclusive than a club is expected to be? Using the economic theory of goods and the experience of the European Union (EU), we show how the loss of exclusivity vis-à-vis outsiders and the increase in rivalry transforms a regional organization from a ‘club’ to a ‘common resource pool’. We also highlight the shift in the governance structure of a regional organisation from ensuring positive net benefits to managing negative externalities. The transformation from a club to a common resource pool requires more self-discipline and greater multilateral surveillance. The experience of membership changes fundamentally as a result.
