We study the impact of scope-of-practice laws in a highly regulated and important policy setting, the provision of medication-assisted treatment for opioid use disorder. We consider two natural experiments generated by policy changes at the state and federal level that allow nurse practitioners more practice autonomy. Both experiments show that liberalizations of prescribing authority lead to large improvements in access to care. Further, we use rich address-level data to answer key policy questions. Expanding nurse practitioner prescribing authority reduces urban–rural disparities in health care access. Additionally, expanded autonomy increases access to care provided by physicians, driven by complementarities between providers.