The issue of overriding mandatory rules is a common topic in the area of private international law. It concerns rules that apply to private law relationships with an international element regardless of the otherwise applicable law. This article researches overriding mandatory rules, their distinctions from mandatory rules, their applicability from the perspective of the trying forum, their connection to the public policy exception, the application of overriding mandatory rules, and observing their effects. The following part explores international codification of overriding mandatory rules, mainly a Rome I Regulation. The appropriate CJEU case law is commented in detail in Ingmar C-381/98, Unamar C-184/12, Nikiforidis C-135/15, Verein für Konsumenteninformation C-191/15 and C-272/18, Agro C-507/15, and Da Silva Martins v Dekra C-149/18. Towards the end, the author reflects upon whether a legal regulation of overriding mandatory rules in national law is still meaningful or whether the time has come for a new solution.