A large literature studies why firms self-regulate and “signal green.” However, it has ignored that regulators have enforcement discretion, and may act strategically. We fill this gap. We build a game theoretic model of whether a firm should signal its type through substantial self-regulation. We find self-regulation is a double-edged sword: it can potentially preempt legislation, but it can also lead regulators to demand higher levels of compliance from greener firms if preemption fails. We show how self-regulatory decisions depend upon industry characteristics and political responsiveness to corporate environmental leadership. We have made a number of simplifying assumptions. We assume activist groups cannot challenge regulatory flexibility in court, and that regulatory penalties are fixed and are not collected by the regulator. Firms with low compliance costs confront a tradeoff regarding self-regulation. They can blend in with the rest of the industry, and take few self-regulatory steps. This reduces the risk of regulation somewhat, and preserves their ability to obtain regulatory flexibility should regulation be imposed. Alternatively, they can step up with substantial self-regulation. This better mitigates the risk of regulation, but at the risk of signaling low costs and becoming a target for stringent enforcement should regulation pass. Recent work has found negative market reactions to corporate claims of voluntary emissions reductions, despite the conventional wisdom that it “pays to be green.” We offer a new explanation to scholars and managers: regulatory discretion may undermine the ability of industry self-regulation to profitably preempt mandatory regulatory requirements.