David Cameron is absolutely right when, not only in the context of "Brexit", he says that Britain has a Veto right in the EU and could stop Turkey joining the European Union, but this right is like a double edged knife !
Every country has the same right when, for example, fundamental principles in EU Treaties need changing. This is why at present the EU is incapable of even slightly updating Treaties. There must always be 100% agreement by all countries ! Is this practicable ?
Controling EU frontiers and immigration are but two prime examples where EU laws have been abandoned and piecemeal solutions have been "permitted" !
These measures are perhaps "temporary", but they reveal what is wrong in the EU at present and what really must be addressed in the near future.