Despite several years since the full implementation of the “narcomenudeo reform” in Baja California, we found dismally low levels of legal knowledge of its decriminalization provisions among police officers in Tijuana. These results underscore the failure of an effective rollout of the reforms in that locale. The PEP effect measured here was associated with a dramatic increase of the participants’ technical and conceptual legal knowledge related to decriminalization for marijuana, heroin, and methamphetamine, as well as the legality of syringe possession. Predictably, officers were somewhat less successful in correctly recalling the law’s precise technical provisions. Our findings suggest that the effort to maintain minimum educational requirements [47] (i.e., high school diploma) may improve the uptake of trainings such as the PEP described here. The use of a standardized test measuring educational performance could also help incentivize improved instructional coverage and learning tools among police officers. International literature reflects growing recognition of the importance of PEPs to inform police practices targeting vulnerable groups [48, 49]. In evaluating the legal knowledge element of the PEP, this study adds to this emerging evidence base and highlights the successes, challenges, and opportunities of harm reduction-focused police instruction [50].

While many policy changes regarding drug policy and public safety in Mexico lack a theory-driven approach, the “narcomenudeo reform” case underscores the need for better empirical understanding of the targeted objectives, operational resources, and a more effective policy evaluation framework that includes public health goals. Our previous analysis suggests that the implementation of operational components of the reform are close to non-existent in Tijuana [32]. Using partial data from freedom of information requests, other authors have concluded that while federal detentions for drug crimes have increased, this phenomenon has not been reflected in trends on the local level. More studies that triangulate information from drug user, police, and judicial sources could help to better evaluate the impact of the reform [51].

Drug policy reform is often necessary, but not sufficient to achieve public health goals because of gaps in translating formal laws to policing practice [52, 53]. To close such gaps, PEP initiatives bundling occupational safety information with relevant legal content demonstrate clear promise. Since the ESCUDO project seeks to close the gap in the implementation of a harm reduction-oriented policy [38, 52], identifying factors that potentiate better uptake of legal information is critical to better roll out of the law.

Evaluation of past police education initiatives, including those focused on harm reduction content, has noted discrepancies in uptake and receptiveness of trainings based on a number of characteristics. These studies have included demographic factors like age, education level, and number of years working as a police officer, as well as attitudes on harm reduction and other occupational safety factors [5]. Our analysis found that only educational level was significantly associated with legal knowledge improvement after adjusting for other socio-demographic factors. In a novel way, this reframes police professionalization efforts such as mandatory employment standards [54] as potentially instrumental for harm reduction. We have found only one previously published study examining predictors of legal knowledge acquisition among officers, which identified years of police service as a significant predictor for follow-up knowledge intake [55]. Our study, with its large sample size and high participation rate, substantially expands the evidence base, with implications for instructional design and tailoring.

Nonetheless, legal knowledge change alone is likely not sufficient to transform drug law enforcement. Structural factors such as deeply ingrained stigma, arrest, and other punitive enforcement incentives and other contributing influences also shape police practices. Nevertheless, it is difficult to see how the harm reduction potential of Mexico’s “narcomenudeo reform” and syringe possession provisions can be harnessed without improving dismal levels of officer knowledge about the black letter law. This alone makes legal knowledge a vital intervention target; specific contribution of legal knowledge, attitudinal, and other training components to behavior change will be explored in future analyses using follow-up cohort data.

Prior police reform in Mexico has shown that local police forces lack the education, resources, and proper accountability controls to do their jobs effectively [56]. In addition, policing strategies might change from administration to administration, in part due to the lack of a strong civil public sector career system which relies more on informal rules or patronage appointments [40]. Efforts to standardize and professionalize policing have taken the form of federal guidelines and subsidies, among others [19]. Street-level officers and management should be involved in planning the reforms, so collaboration with external actors and the police can be successful by combining a rigorous evaluation of the results and adapting them to the realities of policing on a daily basis [56].

The correct implementation of the “narcomenudeo reform” has great potential to shift Mexico’s response to substance use to one rooted in public health rather than in a counterproductively punitive approach. The differentiation of drug possession levels between users and traffickers could theoretically help the criminal justice system to optimize its resources by transitioning from an aggressive police enforcement model to a more harm reduction-oriented approach contemplated by the “narcomenudeo reform.” However, our findings indicate that such policies require additional efforts to assure police compliance with the letter and spirit of the laws. The successful experience of the Portuguese reform could help to motivate police management to embrace drug decriminalization as a way to reduce the burden of drug-related harms on the criminal justice system. Portugal saw a decline in costs associated to the imprisoning of drug offenders, overcrowded jails, and reducing the time officers spent in dealing with drug offenses instead of solving high impact crimes [57].

It is imperative to reconsider the drug volumes deemed reflective of typical personal consumption amounts established by the reform. As demonstrated in other cases around the world, the thresholds for personal possession must be meaningful, closely related to the market realities, and in no situation should they lead to arrest or criminal prosecution [17]. As expressed by other observers, the setting of artificially low threshold quantities might expose casual consumers to excessive criminalization Others have posited additional theoretical unintended harms, such as consumers being incentivized to purchase larger amounts to avoid frequent contact with drug dealers [37]. It is also worth noting that decriminalization schemes vary around the world, and there are many other factors at play other than the threshold quantities, such as the role of medical professionals, the institutional capacity of the judicial sector, or the existing social norms toward drug use, that must be taken into consideration to create an effective model [17].

The foundation of this project was a unique collaboration between an academic institution and a police department, including its training academy. The partnership between UCSD and the SSPM Tijuana, the first study of its kind in Latin America, offers valuable lessons that could shape police training, practices, and drug policy implementation in Mexico and elsewhere across the region and globally. Sustainable collaborations between academic institutions and local governments are critical to long-term strategies for police reform and institutionalizing a synergy between two areas that have traditionally operated in isolation from one another, police and public health.