This chapter explores the implications of a circular economy for law, particularly with respect to plastics. Reflecting that our thinking about circular economies has emerged only in recent decades and that it is still evolving, this chapter aims principally to map out key aspects of the debates about law’s role in the circular economy. However, some normative claims about how law should address the circular economy are advanced, and, in particular, the argument that holistic, systems-based approaches are required to enable a circular economy. If a circular economy is about preventing harmful escapes of plastics from economic systems, then laws must support something akin to a closed system - one with no ‘regulatory gaps’ that permit undesirable escapes from the circular economy. This chapter proceeds in four Parts. In the second Part of this chapter, the meaning of circular economy is investigated. This shows the circular economy to be a complex and contestable idea; one that applies to different things in different ways. Accordingly, a holistically focused framework concept of the circular economy is advanced which indicates what needs to be pursued within regulatory regimes. Part Three looks at legal perspectives on the circular economy literature, providing an overview of how law can enable or impede moves to circularity in plastics use. This leads to an assessment of a range of legal instruments aiming to advance circular economy approaches in Part Four. Given the connectivity of supply chains and the diffuse impact of plastics on natural systems from the local to the global level, the scope of the review includes references to international, regional and domestic legal regimes. The analysis highlights several challenges, particularly the hidden risks of negative environmental and distributional consequences that may result from an unsystematic approach to regulating for a circular economy. Overall, the chapter indicates that there are several fundamental challenges facing our efforts to improve regulation ...