This Practice Note forms part of a suite of content designed to provide practitioners with the context and conceptual tools they will need when dealing with biodiversity law. It focusses on the role of the courts in the development of biodiversity law, and provides examples of biodiversity litigation. It looks at the application of standard public law principles, the margin of appreciation in cases involving scientific, technical and predictive assessments, the weight given to the advice of an expert national agency, the Aarhus Convention and relevant cost caps, and the role of the Office for Environmental Protection in relation to breaches of environmental law and the monitoring of public bodies.