From the press release (no. 110/25, available in full version at this link):

Advocate General Tamara Ćapeta revisits the Ruiz Zambrano case-law under which static EU citizens, such as V’s son, who have always lived in their Member State of nationality and have never resided in another EU Member State, are nevertheless protected on the basis of Article 20 TFEU.
She argues that citizenship rights include a right to decide not to move to another Member State. Therefore, if a child, who is an EU citizen, would be compelled to leave the territory of his or her Member State in order to accompany his or her third-countr national parent, who is required to leave that Member State, Article 20 TFEU grants that parent a derived right of residence in the State of the child’s nationality so as to protect that child’s right not to move. That is so, even if the minor EU citizen would not be compelled to leave the territory of the Union as a whole, but only the territory of his or her own State.
Before deciding whether to expel a third-country national parent, the competent authorities are required to verify whether the dependency between the child and his or her parent is such that that child would be compelled to accompany his or her parent if that parent were denied a right of residence in the Member State of which the dependent child is a national. In that assessment, those authorities must take into consideration the best interests of the child and the right to family life, protected under the Charter of Fundamental Rights of the European Union.

The opinion is available in full version at this link.

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Traduzione italiana di uno stralcio del comunicato stampa in inglese (n. 110/25):

I diritti derivanti dalla cittadinanza europea cittadinanza comprendono il diritto di decidere di non trasferirsi in un altro Stato membro. Pertanto, laddove un minore, cittadino dell’Unione europea, sia costretto a lasciare il territorio del proprio Stato membro per accompagnare il genitore cittadino di un paese terzo, obbligato a lasciare tale Stato membro, l’art. 20 TFUE conferisce a tale genitore un diritto di soggiorno derivato nello Stato di cittadinanza del minore, al fine di tutelare il diritto di quest’ultimo a non trasferirsi. Ciò vale anche se il minore cittadino dell’Unione europea non fosse costretto a lasciare il territorio dell’Unione nel suo complesso, ma solo il territorio del proprio Stato.

Le conclusioni sono reperibili in versione integrale, in lingua italiana, a questo link.