" it is the right of European Union citizens to enjoy free movement between EU countries without being stopped by border controls. However, how can the border controls know whether you are an EU citizen or not unless they stop you to ask for your EU identification? So it's only by presenting your passport or ID card that you can exercise your right not to have to present your passport or ID card."
Well no, that is not how it works: within the core "Schengen" area, there is freedom of movement, passport is only shown when you enter that zone from outside. Inside it you are free to cross the border between Spain and Portugal etc as often as you like with no passport.
Within that, countries have the right to reimpose a border in certain emergency conditions, or indeed to not join the Schengen zone at all as per the case of the UK which had already opted out of a number of major initiatives such as this.
Biting the hand that feeds IT
