question: BACKGROUND AND AIMS: To prevent COVID-19 transmission, some U.S. federal regulations on substance use disorder (SUD) treatment were suspended in March 2020. This study aimed to quantify the extent of state-level policy uptake and the potential number of people with SUD affected by these policy changes across the U.S., as well as to assess if policy uptake correlated with rates of people with SUD already in treatment or needing treatment. DESIGN: Cross-sectional analysis of policies implemented as of April 13, 2020 SETTING AND PARTICIPANTS: 50 U.S. states and the District of Columbia MEASUREMENTS: State-level implementation of: oral schedule II controlled substances emergency prescription, extended take-home doses for medication for opioid use disorders (MOUD), home-delivery of take-home medications, telemedicine for schedule II-IV prescriptions, telemedicine for buprenorphine prescribing initiation, and waiver of out-of-state DEA registration. Rates per 100,000 population of: adults in treatment for SUD, MOUD treatment at facilities with opioid treatment programs, SUD based on DSM-IV criteria, and needing but not receiving treatment. FINDINGS: Half of states (n=24) enacted no policies, leaving approximately 460,955 people in treatment and 114,370 people on MOUD pre-pandemic uncovered by any policy expansion. Only telemedicine for buprenorphine initiation was marginally associated with pre-pandemic rate of SUD treatment (odds ratio (OR)=1.003, 95% confidence interval (CI)=(1.001, 1.006)) and rate of MOUD therapy (OR=1.006, 95% CI=(1.002, 1.011)) in univariable analysis, but these associations were no longer significant when controlling for state-level demographics. No policies were associated with state-wide SUD prevalence or rate of unmet treatment need (p>0.05). CONCLUSIONS: Twenty-four US states did not implement at least one federal policy for substance use disorder treatment expansion as of April 2020, leaving approximately half a million people in treatment pre-pandemic potentially without access to treatment or risking exposure to COVID-19 to continue in-person therapies.