We study the impact of SEC enforcement on information leakage by corporate insiders. We find, for the first time, that SEC enforcement has a significant and immediate deterrent effect on insider leakage. Furthermore, enforcement actions undertaken after a long period of SEC enforcement inactivity display a more significant effect on leakage, consistent with predictions that insiders adapt their behavior depending on how active they perceive the regulator to be. We also study SEC escalations in sanctioning and find that they have a particularly notable deterrent effect, changing insider leakage behavior for approximately 24 months. Our results suggest that capital markets regulators need to intervene on a regular basis in order to maintain deterrence of undesirable behavior.