This article proposes an original theoretical approach to the analysis of community-level action for sustainability, focusing on its troubled relationship to the sharing economy. Through a conversation between scholarship on legal consciousness and diverse economies, it shows how struggles over transactional legality are a neglected site of activism for sustainability. Recognizing the diversity of economic life and forms of law illuminates what we call ‘radical transactionalism': the creative redeployment of legal techniques and practices relating to risk management, organizational form, and the allocation of contractual and property rights in order to further the purpose of internalizing social and ecological values into the heart of economic exchange. By viewing sharing-economy initiatives ‘beyond Airbnb and Uber’ as sites of radical transactionalism, legal building blocks of property and capital can be reimagined and reconfigured, helping to construct a shared infrastructure for the exercise of collective agency in response to disadvantage sustained by law.