Ilonka Sayn-Wittgenstein v. Landeshauptmann von Wien, Case C-208/09, CJEU (Second Section), 22 December 2010

Non-recognition in the Member State of citizenship of the noble surname acquired in the different Member State as a result of adoption by a citizen of that latter State. No violation of the right to free movement of persons.
 

Art. 21 TFEU

Article 21 TFEU must be interpreted as not precluding the authorities of a Member State from refusing to recognise all the elements of the surname of a national of that State, as determined in another Member State, in which that national resides, at the time of his or her adoption as an adult by a national of that other Member State, when that surname includes a title of nobility that is not permitted in the first Member State under its constitutional law, provided that the measures adopted by those authorities in that context are justified on public policy grounds, that is to say, they are necessary for the protection of the interests which they are intended to secure and are proportionate to the legitimate aim pursued. It does not appear disproportionate for a Member State to seek to attain the objective of protecting the principle of equal treatment by prohibiting any acquisition, possession or use, by its nationals, of titles of nobility or noble elements which may create the impression that the bearer of the name is the holder of such a rank. In those circumstances, such a refusal cannot be regarded as a measure unjustifiably undermining the freedom to move and reside enjoyed by citizens of the Union.