Abstract
This paper explores how Italian local governments are implementing the constitutional principle of subsidiarity in its horizontal meaning through the organisational model of shared administration. Since 2014, this principle has allowed around 280 local governments to collaborate on equal terms with citizens on matters of common interest through institutional support for civic participation through the commons. Based on that, this paper asks whether the Italian case can offer a new perspective to the EU principle of subsidiarity. In fact, the European Union has traditionally understood this principle only in its vertical dimension, referring to the allocation of competences among governmental levels, and not in its horizontal one. By shedding a light on the original debate that introduced the principle within the EU legal order, and by looking at its pre-legal, centuries-old conceptualisation, the paper argues that horizontal subsidiarity constitutes the forgotten meaning of this principle whose traces can be found in the current EU legal order. The rediscovery of this interpretation is particularly relevant for local governments in so far as a horizontal understanding of subsidiarity could strengthen their role in furthering local democracy in multi-level systems.