In 2020, Jussi Jaakkola defended his doctoral dissertation European Economic Integration, Fiscal Interdependence, and the Crisis of the Social and Democratic Tax State. In his dissertation, Jaakkola examined the consequences of European economic integration for national systems of tax law and the relevance of these effects on nineteenth-century interpretations of democratic rule.

Jaakkola's current research focuses on historical interdependencies between law, international economic integration and democratic systems. Jaakkola is interested in the long-term development of political, constitutional and economic ideas in their given historical-cultural contexts. Political legitimacy of taxation is among the core themes in his research.