This article develops and tests a refined theoretical account of de-Europeanisation to assess how well it explains the increasing differentiation of UK environmental policy after 2016. Drawing on an original analysis of relevant policy documents, parliamentary processes and legal reforms, it reveals how policy, politics and polity have changed more significantly than was originally foreseen. It departs from the existing literature by revealing that the devolution settlements of the late 1990s opened up the possibility of not one, but multiple pathways of change ranging from de-Europeanization, through to dis- and active re-engagement. It describes how UK policy – once outside the framework of EU processes and institutions – is being re-shaped via a multi-level negotiation between actors in Brussels, London and the devolved administrations. It concludes that despite conflicting policy objectives across the UK, the predominant pattern of change is nevertheless one of gradual disengagement from the EU environmental rule-book.