The classical debate between numerus clausus and numerus apertus of real rights acquires a distinctive configuration within the context of the Land Registry. While civil law theory traditionally tends to present the catalogue of real rights as closed, the registral perspective qualifies this conception by focusing on determining which juridical situations of a real nature may enter the registry and under what conditions. Under the Spanish Mortgage Law—particularly Article 2.2—and Article 7 of the Mortgage Regulations, the system permits registration not only of the typical real rights but also of “any other real rights” and of acts or agreements of a real nature even if they lack a specific statutory denomination. On this normative basis, a consolidated doctrine has been constructed by the former Directorate-General for Registries and Notaries and subsequently by the Directorate-General for Legal Certainty and Public Faith, which has shaped an authentic registral numerus apertus.
The Resolution of 8 August 2019 constitutes one of the clearest milestones in the formulation of this doctrine. In that decision, the Central Authority expressly affirms that the legal system allows both the creation of new real rights not provided for in legislation and the alteration of the typical content of existing ones through conditions, terms or modes. Nevertheless, this configurative freedom is not unlimited. Private autonomy, in matters concerning real rights, is subject to the need to provide a sufficient justification for the creation of the right, to ensure the precise determination of its boundaries—particularly relevant to the protection of third parties and the operation of the principle of speciality—and to comply with the basic structure of the system so that the atypical figure does not contravene the logic of property transactions. The resolution, therefore, not only recognises the openness of the system but also defines its essential limits.
The same approach is evident in the Resolution of 29 August 2023, in which the Directorate-General analysed a complex figure relating to superstructure and substructure building rights configured by the parties. Although the appellant correctly invoked the open nature of registrable real rights—relying on Articles 2.2 of the Mortgage Law and 7 of the Mortgage Regulations—the Authority ultimately refused registration on the ground of infringement of the principle of speciality. The configuration proposed produced, in effect, a material confusion between architectural units and registered parcels that made it impossible to delineate clearly the content of the claimed right. This decision reaffirms the existence of a numerus apertus while emphasising that such openness requires atypical figures to be structurally compatible with the mortgage system and drafted with absolute precision as to their object and scope.
This interaction between openness and technical rigour is complemented by the doctrine set out in the Resolution of 11 July 2022, which, although concerned primarily with formal aspects of mortgage loans, clarifies the relationship between the material title under Article 2 of the Mortgage Law and the formal title required under Article 3. According to the Directorate-General, registration of any real right—whether typical or atypical—requires not only that it be grounded in a valid juridical act coherent with the structure of the system but also that its full content be incorporated into a public instrument enabling the Registrar to exercise his or her duty of legality control. Material openness does not relieve the parties of strict compliance with the formal and publicity requirements inherent to the registral system.
The combined analysis of these resolutions makes it possible to identify a clear model: the Spanish Land Registry operates under a numerus apertus of registrable rights, but one that is strictly conditioned. The creation of new real-law configurations, as well as the modification of the content of typical rights, is permitted provided that a legitimate cause exists, that the right is precisely delimited, and that its configuration does not generate uncertainty or distort the institutional architecture governing real property. Freedom of contract is therefore acknowledged, but is channelled through the essential principles of the mortgage system: speciality, legality, publicity and protection of reliance in property transactions.
The result is a system that combines the flexibility required by contemporary economic needs with a high degree of technical precision and legal certainty. The Land Registry is not a closed catalogue of statutory figures, but rather an adaptable instrument capable of receiving innovative real-law configurations, provided they fit harmoniously within the structure of the legal order and contribute to transparency and clarity in property transactions. This synthesis of controlled openness represents the most coherent and robust position of contemporary Spanish registral doctrine.