It is common to enrich legal debate with the principles of good governance or with data regarding the nature of goods or of services. Much less frequently, however, do we see the question of influence in the opposite direction: whether, in interdisciplinary research, it is the study of the commons that could gain from the application of legal constructs. I see such an opportunity in the interdisciplinary research on bundles of property rights. Law and the study of the commons operate on similar territory which in the commons research is centered around collective action, and in private law focused on the idea of contract. What unites both fields are the common phenomena of collective action, which happens even in a group of two members only, and the social dilemma of sharing goods and services. The study of the commons treats contracts as, at best, merely one of the de jure sources of property rights (in rem rights) to the resource, but a close study shows that arrangements in personam as seen operating especially in Roman law, but also in common law and civil law tradition, have, by contrast, much in common with de facto rights which originate among resource-users finding themselves at the bottom of collective action. In personam arrangements with a lower level of protection from third parties emphasize the principle of inclusion, while in rem arrangements representing strong property rights favor the principle of exclusion. Thus, in personam arrangements primarily serve to promote cooperation for governing the commons, including within a group of in rem rights holders.
