People with criminal justice system involvement (i.e. who have been to prison for a criminal offence) are more likely to use drugs like heroin and methamphetamine compared to the general population. People who use drugs also are at higher risk of negative outcomes like overdose and more rapid or frequent return to prison. Efforts to address overdose, both in prisons and in the community, have been focused on providing treatment for people who use opioids (e.g. heroin, fentanyl). This alone may not be sufficient to reduce overdose risk, particularly among people who use other substances (e.g. cocaine, alcohol) in addition to opioids. In March 2020, in the context of COVID-19, the British Columbia (BC) Ministry of Health provided new Risk Mitigation Guidance (RMG) for doctors, permitting them to prescribe opioids, stimulants, benzodiazepines, and alcohol withdrawal management medications to people at risk of overdose. In this study, I will evaluate whether the RMG has reduced overdose and return to prison among people with criminal justice system involvement in BC. This study will highlight gaps in substance use services in BC, and will inform evidence-based services that can help to reduce overdose in prison and community.