Disentangling the instruments, scope conditions and mechanisms of regulatory peer review – A study with a special focus on different types of national regulators within the European railway sector

The EU seeks to address a regulatory gap by promoting horizontal cooperation among national regulators through European Administrative Networks. While research highlights peer learning, it overlooks regulatory peer review. This paper contributes by theoretically disentangling the instruments, mechanisms and scope conditions for regulatory peer review. Furthermore, it presents an illustrative case study of the European railway sector to study how these elements manifest in practice. Drawing on a document analysis and 28 expert interviews, this study indicates that complete, partial and basic instruments coexist, differing in formalization and administrative consequences but all contributing to informal comparison and national regulatory decision-making. Furthermore, voluntary network participation, the predominance of constructivist-oriented mechanisms and regulators’ independence limit the manifestation of informal sanctions and the emergence of ad hoc RPR. Resources are identified as a fourth scope condition and greater formalization at the supranational level may be necessary for regulatory peer review to develop effectively.