On 9 October 2018, the Civil Division of the The Hague Court of Appeal in the Netherlands has delivered its judgment on the appeal of the ‘Urgenda case’ The Court imposed an order to act on the Dutch government to adjust its policy from 20% to achieve a 25% emission reduction by 2020, compared to 1990 levels (paras 51 and 75). The judgment confirmed the initial ruling in favour of Urgenda in 2015.[i] The consequences for Dutch climate, energy and environmental policy and potentially for climate mitigation efforts worldwide are potentially far-reaching, regardless of possible further appeals by the Dutch government. This ruling raises important questions with respect to the interpretation of Dutch and European Union law, their interrelationship, and possible transferability to other national jurisdictions. In this Commentary, we discuss these issues in turn, starting with a brief synthesis of the judgment.