The article deals with some crucial legal conceptual features related to the public debate on the commons. As alternative to both private and public property, the commons call into question a vast array of practices and concepts that built the Western legal tradition. Concepts such as unavailability, public service, and use are mobilized in order to show the existence of a hidden though strong tradition of management - the ancient administratio - which is considered to be the best suited for the government of the commons. The concept of use, in the light of an administrative law which is far enough from the classical Weberian account, is considered then the possible hinge between the novelty embodied by commons and their possible juridification.