The development of international law in South and Southeast Asia exemplifies myriad ideological strands, historical origins, and significant contributions to contemporary international law doctrines’ formative and codification processes. From the beginnings of South and Southeast Asian participation in the international legal order, international law discourse from these regions has been thematically postcolonial and substantively development-oriented. Postcolonialism in South and Southeast Asian conceptions of international law is an ongoing dialectical project of revisioning international legal thought and its normative directions — towards identifying, collocating, and applying South and Southeast Asian values and philosophical traditions alongside the Euro-American ideologies that, since the classical Post-Westphalian era, have largely infused the content of positivist international law. Of increasing necessity to the intricacies of the postmodern international legal system and its institutions is how the postcolonial project of South and Southeast Asian international legal discourse focuses on areas of international law that create the most urgent development consequences: trade, investment, and the international economic order; the law of the sea and the environment; international humanitarian law, self-determination, socio-economic and cultural human rights.