Rights-Based Constitutional Jurisprudence and the Limits of Planning Theory: The Asymmetric Paradigmatic Transformation of the Turkish Constitutional Court, the Interpretative Ground of Proportionality and a Comparison with German Constitutional Law

Background: In a January 2023 symposium speech, Zühtü Arslan, President of the Turkish Constitutional Court, stated that Turkish constitutional adjudication had moved from an ‘ideology-based approach to a rights-based approach’. This institutional self-description names a thirty-year evolution in the case law, from the 1989 headscarf annulment ruling to the 2019 Zübeyde Füsun Üstel and Wikipedia rulings. It does not, however, account for that transformation at the level of legal theory. How does institutional history shape the law, and what grounding mechanism can explain a shift in constitutional case law? This study asks which theoretical model best explains the transformation in question within the ‘grounding’ debate in contemporary legal theory. It links this question to broader discussions of judicial reform in post-authoritarian and transitional legal systems. Method: The study combines doctrinal (dogmatic) legal analysis with a comparative approach. Eight decisions of the Turkish Constitutional Court (the 1989 headscarf ruling, Zübeyde Füsun Üstel, Wikipedia, Şahin Alpay, Mehmet Hasan Altan (2) and (3), Kavala (1) and (2), and Ahmet Şık (2)) were analysed on an ‘extreme case’ selection logic; six canonical judgements of the European Court of Human Rights (ECtHR) served as a benchmark for comparison. The theoretical framework rests on Scott Shapiro’s planning theory, Nicos Stavropoulos’s reframing thesis, and Mark Greenberg’s moral impact theory. The study examined Turkish constitutional doctrine through eight standard works and German constitutional law through Kommers and Miller’s reference work. Results and Conclusions: The study presents four findings. First, the study empirically demonstrates the paradigmatic shift by comparing contrasting extreme cases. Second, the transformation is not homogeneous: the state-of-emergency rulings preserve the paradigm, the Kavala rulings mark a regression, and the 2025 Ahmet Şık (2) ruling shows continued resistance at the Section level. We conceptualised this pattern as ‘asymmetric heterogeneity’. Third, the transformation cannot be explained with the conceptual tools of Shapiro’s planning theory; the ‘constitutional delegation’ defence also falls short. Fourth, the concrete structure of proportionality review can be understood as the institutional expression of an interpretivist grounding model converging with Greenberg’s moral impact theory and Berman’s ‘principled positivism’. This conclusion offers a theoretical basis for a more transparent style of reasoning in Turkish constitutional adjudication, suggests that openly acknowledging the moral dimension of proportionality review would strengthen judicial accountability, and proposes a generalisable conceptual framework (asymmetric heterogeneity) for analysing paradigmatic shifts in constitutional courts in transitional contexts.