The mobilization of law to address the degradation of the environment implicates a wide range of institutions, actors, and materials. This article maps developments in the study of environmental legal mobilization. It examines the different theoretical approaches that account for why and how groups mobilize the law (or do not), including explanations focusing on law; legal opportunity structures; resources; and/or ideas, identities, and knowledge. It then considers some of the methodological challenges of studying environmental legal mobilization and highlights recent efforts to overcome them and broaden the scope of the analysis. The article then identifies four trends that are shaping the mobilization of law: ( a) changing forms of environmental law and regulation; ( b) shifts in the political landscape, including repression of civil society and the undermining of the rule of law; ( c) the growing diversity of the environmental movement; and ( d) the cumulative impacts of environmental and climate degradation on the very institutions, processes, and resources available for the mobilization of law. Expected final online publication date for the Annual Review of Law and Social Science, Volume 18 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.