“10. In short, the error of law is limited to the terms of the assessment of proportionality, in the context of, and its interrelation with, the exercise of discretion. That error does not infect the findings of fact and they are preserved”
‘Rottmann concerned a case where a person had exercised free movement rights to move from his Member State of origin to a host Member State, in other words that there was a cross-border element engaging EU law in addition to the subsequent acquisition and thereafter loss of the nationality of the host Member State. The case did not test the proposition of whether the acquisition by deception and subsequent loss of the nationality of another Member State is within the scope of EU law in circumstances where the person remains within the Member State of origin during the period of acquisition and loss and does not move to that other state.’