Managed care plans, which contract with states to cover three-quarters of Medicaid enrollees, play a crucial role in addressing the drug epidemic in the United States. However, substance use disorder benefits vary across Medicaid managed care plans, and it is unclear what role states play in regulating their activities. To address this question, we surveyed thirty-three states and Washington, D.C., regarding their substance use disorder treatment coverage and utilization management requirements for Medicaid managed care plans in 2021. Most states mandated coverage of common forms of substance use disorder treatment and prohibited annual maximums and enrollee cost sharing in managed care. Fewer than one-third of states forbade managed care plans from imposing prior authorization for each treatment service. For most treatment medications, fewer than two-thirds of states prohibited prior authorization, drug testing, "fail first," or psychosocial therapy requirements in managed care. Our findings suggest that many states give managed care plans broad discretion to impose requirements on covered substance use disorder treatments, which may affect access to lifesaving care.