This is a particularly thorny issue for those with children born a broad, whilst in the Services. Our daughter was born in Italy in the early 2000s, in a US Naval Hospital and we thought we had correctly registered her through the BFG Registrars' office at the time. Passport duely granted and so on. However, when I went to get a new passport for our last Post, it transpired that she had only been given 'Protected Status' and not full UK citizenship. When I chased this up it was due to me being dual-national, apparently. We've managed to get it sorted out, for the moment at least. Edited to add that it seems that my daughter could now get an Italian passport - which is probably no bad thing.
But it was only a year ago I was asked by MOD (HOCS Sy) - again - to surrender my 'foreign' (FVEY) passport to get access to DII-S. The funny side is that in that job I have access to other, higher, UK systems, and had done so without issue for several years. grown-ups in the FCO put HOCS Sy right.
So, in sum, these problems, at least in my case, were nothing to do with the EU; rather to poor interpretation of the rules by the MOD.
Last edited by Whenurhappy; 16th Jun 2016 at 07:46.