In particular, EU citizens who have never exercised their right of free movement cannot invoke Union citizenship to regularise the residence of their non-EU spouse.

The Court states, that the directive relating to freedom of movement for persons determines how and under what conditions European citizens can exercise their right to freedom of movement within the territory of the Member States. Mrs McCarthy, a national of the United Kingdom, is also an Irish national. She was born in the United Kingdom and has always resided there. Following her marriage to a Jamaican national, Mrs McCarthy applied for an Irish passport for the first time and obtained it. She then applied to the British authorities for a residence permit, as an Irish national wishing to reside in the United Kingdom under European Union law. Her husband applied for a residence document as the spouse of a Union citizen. Those applications were refused on the ground because Mrs McCarthy could not base her residence on European Union law and invoke that law to regularise the residence of her spouse, since she had never exercised her right to move and reside in Member States other than the United Kingdom.

Although Mrs McCarthy born and lived in the UK, the Court found no evidence that it has exercised its right of free movement imposed by the directive relating to freedom of movement for persons directive. Furthermore, EU citizens residing in the Member State of their nationality even if they have another European passport, they enjoy an unconditional right of residence in that State.

Therefore, the Court rules that, in the absence of national measures that have the effect of depriving her of the genuine enjoyment of the substance of the rights arising by virtue of her status as a Union citizen or of impeding the exercise of her right to move and reside freely within the territory of the Member States, the situation of Mrs McCarthy has no connection with European Union law and is covered exclusively by national law. Thus, Mrs McCarthy cannot base her residence in the United Kingdom on rights associated with European citizenship.

This decision is similarly binding on other national courts or tribunals before which a similar issue is raised.