The federalism dimension of proportionality

EU Treaties contain an arsenal of purpose-defined and ambiguous competences that are enjoyed by EU institutions, yet devote little attention to the restraining impact of EU competences on Member States' autonomy and policies. While the focus has traditionally been on subsidiarity to deal with competence issues, the judgment of the Bundesverfassungsgericht in Weiss revitalises the discussion on the potential of proportionality to guide competence issues. This inquiry seeks to highlight both the existing traces of competence proportionality employed by the Court to allocate competences as well as the potential of the proportionality standard to temper the spillovers on Member States' autonomy accruing from the exercise of EU competences. While the Treaty restricts proportionality to reviewing the use (not existence) of EU competences, the Court has implicitly employed proportionality considerations to verify the existence of EU competences. In addition, drawing from established case law, competence proportionality assessments could rely on an effect-based substantive review in combination with procedural duties allowing a meaningful balancing of national autonomy against the dynamics of deeper integration.