The day-watchman regulatory model refers to a balanced regime where the regulator is a cautious observer who creates the rules of the market game, provides information to market participants, and enforces the rules through sanctions. In the AI-driven era, the regulator-watchman is an important factor in the protection of consumers and the regulated area against crises, misconduct, frauds, and systemic failures—“regulatory fires”. This requires building a position of trust, representing neither an active state’s involvement in the market nor a full withdrawal from it. In this light, the chapter draws an original parallel between the Railway Fire Protection Association’s (RFPA) 1925 Handbook recommendations on watchman, as outlined by the National Fire Protection Association (NFPA), and contemporary regulatory discourse on AI. On this basis, this chapter addresses the day-watchman regulatory framework and applies it to a concrete example: the European Artificial Intelligence Office (AI Office) established by the European Union in 2024 for the needs of the Artificial Intelligence Act. Based on its roles and responsibilities, the AI Office aligns with core elements of the day-watchman regulatory framework, such as objectives, enforcement, and monitoring, with some aspects that differ due to the AI Office’s specific focus and legal position.