The numerus clausus of property rights

The numerus clausus of property rights is one of the fundamental principles of property law. It refers to the idea that both the number and content of property rights is limited and is traditionally placed in contrast to party autonomy, which reigns in contract law. Parties can only shape their property rights when they stay within the boundaries provided for by the legal system. Such boundaries are provided by both legislation and case law. Numerus clausus can be understood as a principle, but also as a rule, depending on how strictly it is applied. It can be viewed from a legal perspective, but also from a constitutional or economic point of view, which enhances understanding of why the idea of numerus clausus exists as well as understanding of how it is supposed to function. Numerus clausus also plays a different role within a legal system than it does in respect to the effect of foreign law. There numerus clausus becomes a defensive mechanism. With this more thorough understanding, the practice of numerus clausus can be examined. How do we know a numerus clausus exists and which property rights are part of the numerus clausus? Various authors have argued for a less rigid approach to numerus clausus, possibly looking at ex post control rather than ex ante rigidity. They connect the need for flexibility to the increasingly dynamic nature of property law. Much has been done to discover why numerus clausus exists, but not so much on what role it can play in the future development of property law.