The paper deals with planning norms in action, assuming that planning regulation is one among many kinds of regulation with which planners must contend. Norms operate and co-evolve within a normative ecology where institutions collaborate and compete through overlapping and often incommensurate normative frameworks and rules of the game. The importance of socio-materiality in how different regulations work in practice is emphasized. To develop the normative ecology argument, a case study is presented on the effects of Airbnb tourism on the historic center of Napoli in southern Italy.