Brexit and environmental law constitutes one of the most challenging areas of the divorce negotiations by the United Kingdom. In many ways, EU environmental law developed organically in areas where EU member states felt that common standards would be useful because differing standards would have a direct effect on the internal market. It is also one of the areas that was decisively shaped by the United Kingdom through the introduction into environmental legislation of market mechanisms previously unknown to the administrative legal systems of civil law that governed continental Europe. As such, this area is perhaps more difficult to negotiate because the expectation would be that the United Kingdom will still trade with the European Union, but perhaps intends to lower its own environmental standards, which would in turn give the United Kingdom a competitive advantage. The paper analyzes the impact that the United Kingdom had on the development of EU environmental law.