Institutions are more than mere agents of their creators. They produce unintended consequences by means of their autonomous action. In the context of the European Union (EU), supranational institutions, such as the European Court of Justice (ECJ) and the European Commission produce such consequences, even in areas where no direct or overt transfer of powers has taken place, while performing the roles assigned to them by their creators. Using a case study regarding the protection of the free movement of workers, this article demonstrates that supranational institutions circumscribe the use of executive discretion by national governements by blurring the line between ‘safe’ and other issues, that is, the line that distinguishes between the ‘two faces of power’.