Abstract
Sub-federal units increasingly engage in international trade politics, a policy domain that is an exclusive jurisdiction of the federal level in most federations. This article conceptualizes this process as an instance of federalization, that means a shift from a mode of governance in a policy domain previously dominated by the federal level towards a mode where both tiers are simultaneously active. While the federalization of trade policy seems to be a more general trend across federal systems, the patterns of sub-federal participation and, eventually, the power of sub-federal units to shape trade policy differ significantly. Building on insights from a collaborative research project, this article discusses the causes of sub-federal mobilization and how the institutional configuration of federalism affects sub-federal units’ options to influence trade policy agreements. In the final section, the article speculates about the conditions that may reinforce or undermine this trend in the future.