We argue that proactive law can help organizations be more sustainable. Toward that end, this Article first summarizes proactive law literature as it pertains to corporate sustainability. Next, it examines a series of cases on the pivotal nexus between proactive law and corporate sustainability. It then advances novel propositions that connect proactive law to central organizational design elements. The discussion traces further implications and suggests fruitful avenues for research and ways of using proactive law for firms to become more sustainable. Full article.