On June 27, the U.S. Supreme Court unanimously ruled that doctors who act in subjective good faith in prescribing controlled substances to their patients cannot be convicted under the federal Controlled Substance Act (CSA). The court's decision, which was handed down in Ruan v. United States, is an important decision for doctors who have been convicted of, or who may be at risk of being convicted of, violating the CSA in connection with the nation's opioid crisis. Under federal law, licensed physicians are permitted to dispense controlled substances for "legitimate medical purpose" as part of their professional practice. Consequently, the justices were faced with deciding how to distinguish valid medical conduct from illegal overprescription of highly addictive drugs like opioids.