Abstract
Appeared almost twenty years ago in the doctrinal discourse of administrativ law, still today the term of externalisation is paradoxically not very present in the theoretical language of lawyers, and nearly absent in the positiv law and in the courtrooms. Indeed it is employed most of the time as a « cosmetic » and ideological term mainly destined to realize, generally, of the managerial turn borrowed by organization and management of administrative action in the framework of state reform, and under the influence of the New Public Management precepts. However, it is not dedicated to remain simply as an idiom representative of emergence of a new posture of state and public authorities. As it happens, it can be considered as a concept in full integrated to the general theory of administrativ law. As such, it offers opportunity of an original approach of contemporary transformations crossing this disciplinary purview, and allows to provide a definition and a contents properly administrative to this term many times mentioned and so litte specified. Inspired by the achievements of economics and management, and the works conducts by civil law doctrine, the conceptualization of administrative externalisation leads to the discovery of an novel management mode of administrative action based on a logic of cooperation, and covering the recourse by public authorities at traditional juridical instruments endued of a singular function to empower a third party to share in the realisation of an ability assigned to them by the legal order. Thus elaborated, the administrative externalisation concept unflods in the framework of fulfillement of the concret public authorities ability, under multiple juridical forms and in various fields of activity, by the means of an instrumentalization of the obligation revealing a renewed conception of this one. Therefore, it brings unprecedented elements of understanding of evolution of methods of intervention by the administrative authorities. From title to subtitle, theoretical utility of this concept is measured so in terms of the content assigned to it, wich sets the milestones of an administrative externalisation theory and, beyond, of a cooperative management of administrative action theory.