L’incerta nozione di terzo nel diritto amministrativo. L’esempio della vicinitas

This paper examines the uncertain notion of the “third” in administrative law, highlighting the theoretical and practical difficulties involved in identifying those subjects entitled to challenge administrative action. Traditionally, the category of third parties has been defined in broad and insufficiently rigorous terms, encompassing a wide range of both legal and factual positions linked only by their connection to the exercise of public power. By focusing on the notion of vicinitas, frequently invoked in fields such as planning and competition law, the paper brings to light the tensions between an objective conception of administrative proceedings and the constitutional paradigm centred on the protection of subjective legal positions. It therefore explores the criteria of qualification and differentiation, and considers whether these criteria may provide the basis for a more coherent and rigorous reconstruction of the third party’s legal position in administrative law.