With the number of innovative measures ranging from green certificates for boosting green electricity production to the circular economy aiming at reducing waste, the European Union’s environmental policy has been gathering momentum. What is more, the recent Dieselgate scandal sheds the light on the hurdles facing car manufacturers to meet the Euro 5 and Euro 6 NOx emissions standards. A central feature of EU’s environmental law is its multi-level character. Another is its uncanny relationship with the internal market. Given that, at the core of the EU integration process, lies the internal market underpinned by the principle of free movement – removal of obstacles to free trade and free competition – the relationship between economic integration and environmental protection has always been fraught with controversy. This chapter is an attempt to explain how the free movement of goods within the single market and national environmental product standards could be reconciled in the EU.