We use a novel data set within an instrumental variables framework to test whether the presence and language of constitutional environmental rights influence environmental outcomes. The outcome variables include Yale's Environmental Performance Index and its components. We employ two‐stage least squares to account for reverse causality, that is, the possibility that a country which takes steps to protect the environment might also be more likely to constitutionalize environmental rights. Our first stage theory combines constitution norms, opposition costs, and generation effects. Our controls include country income, which means that our study is also related to the Environmental Kuznets Curve literature. We find that constitutions do indeed matter for positive environmental outcomes, which suggests that we should not only pay attention to the incentives confronting polluters and resource users, but also to the incentives and constraints confronting those policymakers who initiate, monitor, and enforce environmental policies.