To the extent that international trade and development policy employs legal methods, institutions and participants, there is a need to take into account the role of legal culture. There are many different legal cultures in the world, including the widely found common and civil law traditions, as well as the many non-western legal traditions and sub-traditions found within the hundreds of different legal systems spread across the globe. International law has, however, traditionally eschewed consideration of legal culture-arguing that international law is unique, is sui generis, and as such domestic legal traditions were not relevant. Yet, the humans involved in creating and nurturing international legal fields and institutions will themselves reflect the legal culture of their home states, and will often import aspects of those legal cultures into international law. The same must be true of international development law. In addition, international legal fields, such as international development law, must often work within domestic legal systems, and as such they will directly interact with the domestic legal traditions. It is thus important to understand the interaction between the legal cultures reflected in the relevant part of that international law and in that of the domestic legal system. Such an understanding can be useful in ensuring the effective interaction of the two systems. This paper explores these themes, continuing the author's past and ongoing consideration of the role of legal culture in international law, including its role within institutions such as the World Trade Organization.