This commentary provides a legal analysis of the extent to which changes proposed by scholars to promote care for substance use disorder or other under-treated illnesses through risk adjustment could be implemented administratively, without legislation, in federal risk adjustment systems: Medicare's privatized component, Medicare's pharmaceutical component, and the individual and small group market. As the article explains, federal laws governing risk adjustment provide broad discretion to regulators and can reasonably be interpreted to permit full and final implementation through the administrative (...) process of almost all of the changes that scholars have proposed. (shrink)