Urban AI Governance Must Embed Legal Reasonableness for Democratic and Sustainable Cities

This position paper argues that embedding the legal "reasonable person" standard in municipal AI systems is essential for democratic and sustainable urban governance. As cities increasingly deploy artificial intelligence (AI) systems, concerns around equity, accountability, and normative legitimacy are growing. This paper introduces the Urban Reasonableness Layer (URL), a conceptual framework that adapts the legal "reasonable person" standard for supervisory oversight in municipal AI systems, including potential future implementations of Artificial General Intelligence (AGI). Drawing on historical analogies, scenario mapping, and participatory norm-setting, we explore how legal and community-derived standards can inform AI decision-making in urban contexts. Rather than prescribing a fixed solution, the URL is proposed as an exploratory architecture for negotiating contested values, aligning automation with democratic processes, and interrogating the limits of technical alignment. Our key contributions include: (1) articulating the conceptual and operational architecture of the URL; (2) specifying participatory mechanisms for dynamic normative threshold-setting; (3) presenting a comparative scenario analysis of governance trajectories; and (4) outlining evaluation metrics and limitations. This work contributes to ongoing debates on urban AI governance by foregrounding pluralism, contestability, and the inherently political nature of socio-technical systems.