This study examines the transformation of environmental public interest lawyering in China within an ever-tightening legal order, where activists confront both state suppression and co-optation. Utilizing qualitative methods, including in-depth interviews with 49 environmental lawyers and activists, participant observations, and online ethnography, the research delineates two divergent models of legal mobilization. The conventional model prioritizes compliance with state regulations, employing impact litigation and consensus-building with state institutions to drive incremental environmental reforms, often at the cost of aligning with state priorities. In contrast, guerrilla lawyering emerges as an innovative strategy, leveraging decentralized networks, experimentalist litigation, flexible funding, and diffused media tactics to sustain activism while preserving autonomy. By transforming courts into platforms for generating critical information and exposing systemic vulnerabilities, guerrilla lawyering resists assimilation into state-controlled schemes. This approach not only ensures movement survival amidst repression but also enriches theoretical understandings of legal mobilization under authoritarianism by addressing the understudied risk of co-optation. These findings illuminate the resilience and ingenuity of activists in China’s constrained environmental advocacy landscape and offer a transferable framework for resistance for social movements in other authoritarian contexts, amid the global rise of authoritarian legality.