The United States continues to experience a public health crisis related to substance use disorders (SUD) and an overdose epidemic that has only been exacerbated with the COVID-19 pandemic. Medicaid is currently the largest payer of SUD services. Despite this coverage and the availability of evidence-based treatments, most individuals with SUD are currently not receiving treatment. Various states have sought to remedy the lack of access to treatment by requesting Section 1115 authorization to expand SUD services. In this paper, we discuss an analysis we conducted on these waivers and the clinical and legal framework regarding Medicaid coverage of SUD treatment, as well as remaining gaps. We also offer recommendations for improving coverage.