Using the case of the campaign to establish a Supervised Injecting Facility (SIF) and reduce harm for people who use illicit drugs in Dublin, Ireland, this paper makes three related contributions to contemporary literatures. First, by detailing the history of the campaign and paying particular attention to the ways it was influenced by learning from models elsewhere in the world, the paper adds a spatial perspective to research on the intersections of public health and social movements. Second, the paper addresses the policy mobilities literature’s minimal engagement with the role of counter-hegemonic ideas and national states in shaping inter-local policy circulations. It provides detailed empirical analysis of the influence of counterhegemonic ideas and activists’ referencing of those ideas through appeals to empathy, expert evidence, and experience to influence formal state institutions, including the legal system and the national state. Third, the paper addresses ongoing discussions of ‘failure’ in policy-making by arguing for a critical, contextual approach to the spatialities and temporalities of attempts to change entrenched policy and regulatory models. The case study is based on one author’s direct involvement in the campaign for a SIF and on semi-structured research interviews with twelve key actors conducted since 2015. The research also involved an analysis of relevant documentary materials spanning the period 2012-2021 and both authors’ participation in a drug policy forum in Dublin in January 2017, involving local and international actors.