Sweden in the EU: Depoliticization, Politicization, and the Transformation of Parliamentary Conflict

European integration profoundly impacts the executive-legislative relations within national parliaments. However, evidence remains mixed on whether the EU’s impact shifts national conflict dimensions towards depoliticization or increased contestation and politicization. This question is particularly critical in times of heightened polarization, as it affects the EU's legitimacy and the effectiveness of its policies. This study contributes to the literature by examining how the EU's regulatory framework has transformed domestic politics and patterns of opposition within member states' parliaments. We hypothesize that a country's accession to the EU permanently alters parliamentary conflict dimensions, depoliticizing policy areas essential for supranational cooperation while intensifying politicization in predominantly domestic policy areas that remain under national competencies. To test these hypotheses, we analyze unique longitudinal data on committee decision-making for all government proposals in the Swedish parliament over more than 50 years, from 1970 to 2022. Using a difference-in-difference design, we compare the scope and intensity of parliamentary opposition across all policy areas before Sweden joined the EU (1970-1994) and after its accession (1995-2022). Our findings are twofold. First, Sweden’s accession to the EU in 1995 prompted a sharp reduction in parliamentary opposition within economic policy-making that has lasted until the 2020s. Second, our results demonstrate an upturn of controversies in policy areas related to national identity and welfare, where the EU traditionally has limited influence. These results have important implications, demonstrating that the transfer of competencies to the EU has fundamentally reshaped domestic policy-making, creating parallel processes of depoliticization and politicization across different policy areas.