In almost a decade and a half, international environmental law has expanded and matured. But the question remains, ‘Is International Environmental Law fit for purpose?’, as Lavanya Rajamani and Jacqueline Peel point out in their introduction to this second edition of the Handbook of International Environmental Law. When the first edition of the handbook was published in 2007, international environmental law was still a relatively young field. Customary law and treaty law had been applied to selected conservation or pollution issues since the late nineteenth century. But it was not until after the 1972 Stockholm Conference on the Human Environment that modern international environmental law began to grow in earnest, with the 1992 Rio Conference on Environment and Development providing a significant impulse for its further development. Since 2007, international environmental law has acquired ‘breadth, depth, nuance, complexity, and reach’, as Lavanya and Jacqueline note in their introduction. ‘Nevertheless, international environmental law’s achievements in environmental terms’ continue to be ‘modest’.