Drug policy reforms typically seek to improve health among people who use drugs (PWUD), but flawed implementation impedes potential benefits. Mexico's 2009 drug policy reform emphasized public health-oriented measures to address addiction. Implementation has been deficient, however. We explored the role of municipal police officers' (MPOs) enforcement decision-making and local systems as barriers to reform operationalization. Between February-June 2016, 20 semi-structured interviews were conducted with MPOs in Tijuana. Interviews were transcribed, translated and coded using a consensus-based approach. Emergent themes, trends and frameworks were analyzed through a hermeneutic grounded theory protocol. In conceptualizing their orientation towards municipal (not state) law, MPOs reported prioritizing enforcement of nebulous anti-vice ordinances to control PWUD activity. Local laws were seen as conflicting with drug policy reforms. Incentives within the police organization were aligned with ordinance enforcement, generating pressure through quotas and reinforced by judges. Driven by discretion, fuzzy understanding of procedures, and incentives to sanitize space, detention of PWUD for minor infractions was systematic. Failure to harmonize policies and priorities at different levels of government undermine effective operationalization of health-oriented drug policy. Implementation must address local priorities and administrative pressures shaping MPO decision-making and enforcement practice.