This chapter explores the contours of the New Environmental Governance (NEG) approach, mapping the shifts in environmental regulation and governance that led to its development, before highlighting the strengths and weaknesses of NEG for addressing transboundary environmental harms. It develops in the fields of law and governance, rather than within the field of criminology, or more specifically green criminology. The chapter examines much of the NEG work also resonates with the growing focus of green criminologists on broadening definitions of environmental harm, and moving from past-focused processes to forward-looking ones that try to anticipate and prevent the realization of harms. The traditional architecture of national and international environmental regulation arose in the 1970s, against the backdrop of states exercising sovereign ownership over natural resources within their territory. It is therefore logical that early responses to environmental harm relied on the nation state, or at the international level, groups of states, acting primarily through treaty-based intergovernmental organizations.