Abstract
The doctrine of the numerus clausus holds that there is a closed list of forms of property recognised by the common law, new forms of property can generally only be created by legislatures, and new forms of existing property rights will be recognised only if they meet certain conditions. To date, there has been little explicit academic discussion of the doctrine's potential application to trusts but it is suggested that the courts have long applied it, either implicitly or explicitly, in a particularly clear way in two areas. The first is the law regarding prohibitions of restraints of alienation, and the second is that concerning general powers, which are now usually held to be tantamount to property. Both areas bear the imprint of the numerus clausus doctrine in restricting the ability of settlors to tailor the property rights they purport to create under a trust in ways that both harm the coherency of the law and harm the interests of third parties. However, if this is so what in the trust context forms part of the closed list of property forms? After analysing the writings of foundational proprietarian jurists, as well as the jurisprudence of the courts, it is suggested that both legal ownership and beneficial ownership form part of the closed list. Lastly, it is submitted that the numerus clausus is a hidden meta-principle of trust law which prevents the corruption of equitable principles and failing to appreciate this risks leading to serious missteps in the law.