Regulation of nonpoint source pollution often relies in one way or another on policy instruments based on ambient indicators. For well-known reasons, enforcement of ambient-based policies is, at best, limited. If no individual choices or actions are observed, than ambient-based regulation might be the only feasible approach. Often, some relevant individual indicators, such as output or certain inputs, are observable. For such cases, we offer a regulation mechanism that does away with ambient indicators. The mechanism implements the optimal output-abatement-emission allocation and gives rise to the full information outcome when the social cost of transfers is nil. Special attention is given to the regulation of (unobserved) abatement.