Nowhere in EU countries there a requirement for their citizens to _carry_ a legal ID. Some may require you to _possess_ at least a valid one (at home maybe) and all of them require that you are _able to be identified_ by police officers (this means you accept to go to a police station to check your identity).
The first hit when I did:
http://www.iamsterdam.com/en-GB/living/official-matters/comp...
"In 2005 the Dutch government introduced a law to improve public safety stating that everyone must be able to produce valid identification when requested by the police or supervisory officials. Those who fail to produce vailid identification risk being fined. Read on to learn more about valid identification, and to whom the law is applicable."
link (in dutch) http://www.rijksoverheid.nl/onderwerpen/paspoort-en-identifi...
To all the downvoters: please PROVIDE A SOURCE (bill, act, legal review, any language is OK) that states that a citizen of a EU country must _carry_ a legal ID while staying in that country.
Please note I wrote in the original comment and in this comment _carry_, not _provide_.
As I wrote, there are states that require you to _provide_ an ID to police officers. But that doesn't mean that you have to _carry_ it with you all the time, just that you can go back home to take it or go to a police station and be identified there.
The relevant article of the penal procedure code ("Code de procédure pénale"), 78-2, is especially broad: "by any mean" ("par tout moyen").
To my knowledge, the French state does not even require that a French citizen even requests or obtains an identity card or a passport (although having some ID document may be useful in practice).
All anecdotal though and maybe you're right that the letter of the law does not require it. The UK certainly doesn't.
I never had an encounter with the gendarmes in the 5 years I lived there so I never found out first hand.
Edit: looks like you're right. This article does a nice job of breaking it down: http://rue89.nouvelobs.com/2011/12/26/fouilles-controles-did...
(Personally, I always keep my passport with me when travelling abroad.)
In France I always have my ID with me but I know friends who don't (e.g., did not bother replacing a lost ID). Having lived 24 years in France I have never been asked to produce ID by the police or gendarmes. (That said, I am white, not often involved in demonstrations and such, etc.; other people's experiences may vary. :-/)