This study explores the requirement of sustainability in cultural heritage protection from the perspective of constitutionality. Following an indispensable overview of certain concepts relating to its subject it discusses the constitutional framework of legislation on cultural heritage protection. Through an analysis of the applicable legal regulations, it examines the way the Hungarian State can enforce the requirement of sustainability in the specific field of cultural heritage protection. This is, indeed a topical subject, particularly in view of the Act on the Sustainable Development of Certain Elements of Cultural Heritage (hereinafter: “Castles Act”) which was adopted by the Hungarian National Assembly on 12 December 2023, but was not promulgated pursuant to Decision 5/2024. (II. 6.) of Constitutional Court. Ensuring sustainability is, according to the explanatory memorandum attached to the Castles Act is one of the key aspect of the regulation, just like in the case of the act regulating the returning of cultural objects of disputed ownership, kept in public collections.