Economic issues are increasingly integral to the functioning of contemporary governments. This study examines the framework of international law governing trade within the member states of the Economic Cooperation Organization (ECO). The ECO aims to enhance economic development and promote sustainable growth among its members; however, as the majority of its members are developing countries, significant economic and legal inconsistencies persist. Such discrepancies hinder the organization from achieving its core objectives, potentially limiting its overall effectiveness. This study first analyzes trade indices among ECO member states, then identifies the principal determinants of trade, and finally investigates the impact of international investment treaties on the application of international law. The results indicate that, during the period 2003–2015, ECO member states exhibited a relatively low average intra-industry trade index, reflecting insufficient industrial and legal infrastructure. Intra-industry trade levels are considerably lower than those observed in industrialized nations, particularly the European Union, where the average intra-industry trade index reaches approximately 69 percent. Moreover, political dynamics and international relations have further contributed to the organization’s limited efficacy. This article employs a descriptive-analytical methodology, drawing upon reliable documents and empirical data.