Why do non-compliant practices persist after a law is introduced? This paper unpacks variations in regulatory compliance using a social networks lens. Existing literature at the intersection of law and networks largely evokes peer influence as a key mechanism for the diffusion of compliance. But this account falls short of explaining the persistence of regulatory non-compliance. Using a longitudinal network consisting of 312,351 physicians from 2015 to 2017 and a difference-in-difference design, I find that the effects of opioid prescribing legislations are dampened in networks with non-complying peers but amplified in networks with compliant peers. In particular, social pressure from compliant peers is critical for older professionals with stickier practice to abandon overprescribing. The legislation activated stronger peer influence towards compliance in heterogeneous professional networks with some seeds of compliant peers. This paper contributes to the intersection of regulations and social networks literature by showing that peer influence and regulations work in tandem to drive variations in compliance. The implications are two-fold: social reinforcement from compliant peers is key to realizing regulatory efforts; regulation activates stronger peer influence, which helps overcome practice inertia and facilitate compliance. The findings help explain pockets of regulatory compliance and resistance and hold implications for curtailing professional deviance.