The United Kingdom’s decision to leave the European Union will have major consequences for environmental law. EU law is integrated into the UK’s laws in many ways that will be difficult to disentangle and a continuity of laws provision seems desirable in order to avoid gaps in the law appearing. The effect of devolution within the UK is that most environmental matters will in future be the responsibility of the devolved administrations. The UK’s freedom of action will continue to be constrained by obligations in international law, including those establishing a new relationship with the EU. Environmental law in the UK has changed greatly during the four decades of its membership in the EU and most of the innovations introduced through the EU are likely to be retained, although there may be a wish to restore more discretion over the outcomes to be achieved as opposed to having strict obligations to satisfy targets and standards. In structural terms the biggest changes are likely to be the loss of the stability provided by the slow processes of making and changing EU law and the loss of means to call to account the UK government (and devolved governments in Scotland, Northern Ireland and Wales) over their performance in meeting their environmental commitments.