Exploring Assertiveness: How Institutional Architecture and Political Dynamics Shape Constitutional Court Behavior

Why do some constitutional courts frequently annul legislation while others show restraint? Despite broadly similar formal powers, constitutional courts in Europe vary widely in their willingness to strike down contested laws. This paper argues that such variation is not solely driven by legal doctrine or political ideology but reflects the interaction between institutional design and strategic political context. We conceptualize judicial assertiveness as a conditional outcome shaped by how features such as appointment procedures, term renewability, review mode, internal voting rules, and access provisions interact with both de facto independence and the surrounding configuration of political power. Using a new ruling-level dataset of over 25,000 decisions issued by 19 European constitutional courts (1990–2020), we estimate multilevel logistic regression models with random intercepts by country and year. Our findings challenge standard assumptions. Renewable terms are positively associated with annulment - but only in systems with pluralistic appointment mechanisms. A priori review increases the likelihood of annulment, especially when access to the court is highly permissive. The chilling effect of dissenting opinions on assertiveness disappears under qualified majority rules. Finally, courts are significantly more assertive when facing fragmented governments with a strong compliance record, while legislative strength dampens judicial assertiveness. Our results reveal that judicial behavior is not dictated by isolated institutional rules or by context alone. Rather, it emerges from the strategic interplay between institutional architecture and political opportunity structures. Our findings offer a more nuanced account of when and why courts strike down legislation - and caution against one-size-fits-all reforms aimed at empowering constitutional adjudication.