Environmental problems are typically not addressable by the market and private law to redress harm and regulation by the state is the commonly suggested alternative. The public choice perspective on regulation however points to the possibility of regulation not being effective in the light of political capture and corruption in enforcement. Under such circumstances who regulates the regulator? In India the judiciary seems to have taken on this role through an innovation in procedural law namely Public Interest Litigation (PIL). PIL has been lauded as an effective method of ensuring enforcement of regulatory standards. We test whether this holds true in the case of air pollution in New Delhi. We document evidence of regulatory failure and examine whether the series of supreme-court interventions initiated by a PIL have played a significant role in controlling the pollution levels in the city. Autoregressive distributed lag (ARX) models and univariate structural break analysis show that judicial intervention was effective in containing pollution levels.