While compliance with European environmental legislation at the national level has received extensive scholarly attention, the subnational level—where the majority of EU legislation is implemented—remains underexplored, particularly in relation to the role of subnational party composition on subnational compliance. This study thus examines how the presence of green parties in regional parliaments affects the likelihood of subnational compliance with EU environmental requirements. Drawing on original data on subnational infringements from 2005 to 2020, the analysis focuses on Austrian, Belgian, German, and Spanish regions. By adopting a subnational lens, this research provides novel empirical insights into the relationship between multilevel politics and compliance with European legislation, contributing to understandings of multilevel party politics and the political dynamics of European environmental policy implementation.
