This article provides a diagnostic of a major structural problem of environmental law before suggesting a way to address it. The problem is that environmental law, even avant la lettre, was and remains designed as a law of negative externalities: a body of laws fundamentally organized so as to minimize interference with the underlying transaction while mitigating its negative externalities. This article proposes instead to reframe environmental law not as the expression of allocative efficiency but as a means of steering socio-economic processes in directions that are more likely to avoid an irreversible change in Earth System dynamics.