Jaakkola is working on his doctoral dissertation and his research revolves around the historical development of European economic constitution. His dissertation focuses on the transformations of European tax state in the course of European economic integration. On the one hand, the integration has exerted pressure on the viability of national traditions of social and democratic tax law. On the other hand, the European Union has provided a supranational framework within which some of the basic normative ideas on taxation have been reimagined. Without exception, Jaakkola's research interests are closely related to the question of democratic legitimacy and political theory. Furthermore, he is interested in historical and contextual development of legal ideas.