The adjudication of regional and international economic disputes has become the final frontier in the migration of constitutional ideas. The migration of these ideas across different branches of law has become increasingly common, building bridges between different legal systems, furthering judicial dialogue, and allowing judicial borrowing. Scholars, adjudicators and practitioners
“establish a transnational legal discourse and act as merchants of law.”
Against this background, this study investigates the migration of constitutional ideas to regional and international economic law by focusing on the migration of the concept of proportionality from constitutional law to European Union (EU) law and international investment law. The article shows that while the concept of proportionality has analytical merits, it also presents a number of pitfalls when applied to the context of economic disputes.