Trust in the international economic legal order has been associated with an historic global expansion of trade and investment. That trust is at constant, if not imminent, risk of erosion, and may even, in the per¬ception of some, already be in the process of erosion. The interaction be¬tween trust and the notion of complexity may hold the key to understanding that process, whether actual or potential. On the premise of that interaction, an evolutionary interpretation of the transnational regulation of economic private–public relationships as a complex adaptive system may indicate whether and how trust in this context should be restored. The pa¬per sketches the contours of an interdisciplinary research agenda aimed at exploring and investigating the proposition that an evolutionary interpretation of complexity in transnational economic relations may help to situate and explain that complexity and, thereby, to better understand the practical importance of trust in transna¬tional economic regulation.