Temporal effects of decisions of the Constitutional Court of Ukraine: legal certainty and the protection of rights

This article examines the temporal effects of decisions adopted by constitutional courts and the problem of ensuring the effective restoration of individual rights following the declaration of a legal act as unconstitutional. The study aims to identify the optimal model for the temporal effect of decisions of the Constitutional Court of Ukraine, taking into account European experience, and to develop a mechanism that reconciles effective human rights protection with the preservation of legal certainty. The research is based on comparative legal, formal legal, systemic, and doctrinal methods. The study analyses the ex tunc, ex nunc, and pro futuro models, together with the practice of the constitutional courts of Germany, Belgium, Spain, France, Austria, and Lithuania, as well as the Court of Justice of the European Union and the European Court of Human Rights. The findings demonstrate that the Ukrainian model predominantly provides for the prospective effect of decisions of the Constitutional Court of Ukraine, thereby safeguarding legal certainty but failing to ensure the effective restoration of the applicant's violated rights. The article proposes the integration of an evolutionary model of differentiated retroactivity based on the Ergreiferprämie doctrine. Under this approach, ex nunc remains the general rule, whereas the applicant lodging a constitutional complaint is granted mandatory retroactive effect, subject to statutory conditions. Further research should focus on developing legislative mechanisms for implementing this model and establishing appropriate procedural safeguards