Background: In response to the toxic illicit drug crisis, British Columbia (BC) decriminalized possessing ≥2.5g of illicit drugs in January 2023, with the goals of improving access to health services and reducing drug-related stigma and provincial overdose deaths (>13,536 since 2016). Fear of arrest and drug seizure are the most commonly reported barriers to accessing health supports among people who use drugs (PWUD). Drug seizures also affect drug acquisition behaviour, increasing individual overdose risk. Therefore, ongoing evaluation of decriminalization as a harm-reduction strategy requires analysis of changes in police data over-time (pre-decriminalization, decriminalization announced without enactment, and post-implementation). As part of BC’s Monitoring and Evaluation plan, this study will investigate impacts of decriminalization in Victoria. Objectives: Analyze trends in drug possession-related arrests, prosecutions, and convictions (with mean drug weights), across three periods: pre-decriminalization, decriminalization announcement without enactment, and post-implementation. Methods: A seasonally adjusted interrupted time-series analysis of changes in number of drug-related arrests, seizures (with weights), possession charges (simple and for purpose of trafficking), and convictions from Jan-2020 to Dec-2023. Results: Findings will permit testing of hypotheses about the reduction in drug-related arrests for below-threshold possession, by examining events prior to the announcement of decriminalization, between the announcement and implementation of decriminalization, and post-implementation of decriminalization (analyses underway). Implications: Quantifying sociolegal impacts of decriminalization at the street-level will guide policy makers in on-going implementation adjustments and health-systems decision-making.