This special issue introduces a conceptual framework for ethnographies of urban policing that foregrounds how defining features of the city produce police work, and in turn, how police work produces the city. To address how the mutually productive relationship of policing and the city shape current transformations in the ordering of urban space, the notions of borders and bordering are invoked. In contemporary cities across the global North and South, borders and bordering practices are reconfigured to address mobilities and flows deemed to threaten social order and have thus become manifestations of fear and anxiety linked to these mobilities and flows. At the core of our framework is the argument that urban policing is principally a practice of bordering. By approaching urban policing as a practice of bordering that is informed by material and imaginary manifestations, tensions between (de)territorializing and (de)stabilization are highlighted as both the vehicle and outcome of bordering practices. These tensions, we propose, can be captured through the concept of trembling. Trembling implies both a physical and emotional response to anxiety, excitement and frailty that is paradoxically built into borders and bordering practices.