A few months ago the European Commission expressed its criticism on car rental companies. As they would discriminate consumers willing to rent a car online.
It was often impossible to book through another EU country, as consumers were automatically redirected to other pages based on their IP address. As a result, consumers paid a lot more.
The rental companies like Europcar, Hertz and Avis have promised the Commission to not establish barriers so consumers can get the best price.
Read the press release from the European Commission on car hire in the EU.