The United States has seen a precipitous rise in drug overdose deaths in the past two decades, fueled by physicians’ high-risk prescribing. To combat the opioid crisis, states introduced regulations that limit the initial supply of opioids prescribed. What drives physicians’ variation in response to the same regulation? I turn to social networks to investigate this puzzle. Drawing from a patient-sharing networks consisting of 269,542 physicians and 10.6 million initial opioid prescriptions, I find striking distinctions in the social networks supporting the cessation and persistence of high-risk prescribing. Physicians centrally embedded in the network (i.e. who have many connections) were particularly responsive to the regulation and curtailed their prescribing intensity. Importantly, this effect was only realized when the focal physician was out of step with their network. High-risk prescribing continued to persist among isolated physicians or in networks of high-risk prescribers. The results point to peer sanctioning concerns at play for driving the cessation of deviance. This paper contributes to a deeper understanding of the joint effects of social networks and regulations in shaping the abandonment of contentious practices and informs network-based interventions to combat the prescription drug crisis.