In all postfeudal legal systems, the basic ways of owning property are limi
ted in number and standardized in the sense that courts will enforce as pro
perty only interests that are built from a list of recognized forms. In the
common law, this principle has no name and is invoked only semiconsciously
; it is known in the civil-law tradition as the numerus clausus. This Artic
le adopts this term for the corresponding understanding in the common law a
nd advances an information-cost theory that explains the ubiquity and durab
ility of the doctrine.
The numerus clausus can be seen at work in a variety of areas, including es
tates in land, concurrent interests, nonpossessory interests, interests in
personal property, and intellectual property. This Article argues that the
principle serves to reduce third-party information costs throughout the law
of property. Because of their in rem nature, property rights give rise to
third-party information costs in a way that contract rights do not Individu
als trying to avoid violating property rights or investigating whether to a
cquire them need to gather information. Those creating property rights will
in some situations have too little incentive to conform to the most popula
r forms, requiring a degree of mandatory standardization. As it operates in
practice, the numerus clausus strikes a rough balance between the costs of
frustrating parties' objectives on the one hand and the costs of complicat
ing third-party information-gathering on the other.
This Article demonstrates that this information-cost theory provides a bett
er account for the numerus clausus than do alternative positive and normati
ve views, including those based on network effects, sufficiency of notice,
private standards, antifragmentation concerns, and the increasing importanc
e of contract-based rights. Finally, this Article shows that, because it te
nds to preclude judicial innovation in the basic forms of property rights,
the numerus clausus acts as an institutional-choice mechanism that channels
to legislatures the power of innovation in the realm of property rights. I
n keeping with the basic information-cost theory legislative creation and a
bolition of property rights is likely to lead to lower information costs th
an would judicial entrepreneurship in this area.