Conflict of interest regulation in European parliaments: Studying the evolution of complex regulatory regimes

The growing complexity of parliamentary ethics regulation adopted over the last decades makes the systematic examination of its nature and the rationales underpinning regulatory choices an important endeavor. In this paper we introduce conceptualizations and measurements of conflict of interest (COI) regulation directed toward assuring the impartial and unbiased decisionmaking of national parliamentarians. We distinguish the strictness of rules, the nature of enforcement, sanctions, and transparency requirements as core elements defining COI regimes. Applying our framework to 27 European democracies, we select two cases for in‐depth analysis in which legislators chose very different solutions in response to growing pressures to regulate themselves, to inductively explore the drivers underpinning the choice of COI mechanisms: the United Kingdom, which adopted a highly transparency‐oriented regime, and Belgium, which adopted a highly sanction‐oriented COI regime. Echoing neo‐institutionalist perspectives, the longitudinal analyses indicate how the two democracies’ different institutional environments shape distinct answers to similar functional pressures.