This book charts a pioneering course for researchers and policy makers seeking to understand, navigate and influence the decentralised international legal order.

It invites readers on an exploratory journey that treats international trade, investment and tax law as laboratories for the application of the complexity framework to public international law. It describes familiar international legal regimes in unfamiliar terms by shining a light on trade, investment and tax as living sub-systems inside a self-organising network.

Drawing on the vocabulary and metaphors of the complexity framework, such as emergence, feedback, attractors and path-dependency, the book explores why treaties proliferate, why some legal reforms stagnate and others cascade, and where small, well-placed interventions can redirect the whole. Moving beyond descriptive frames, the book supplies a predictive lens and a practical toolbox for steering international law, for example, towards increased resilience. A rich repertoire of examples and vivid metaphors show how legal evolution is shaped. The book's critical reflections keep the promise of complexity grounded in normative debates.

Written for readers with only a basic background in the regimes that govern international economic relations and no prior knowledge of complexity, the book introduces a novel frame of reference to the study of public international law. This book is written for anyone worried about incoherence, fascinated by interconnectedness, and searching for levers of change.