Questione giuridica chiave
Whether the federal office had standing and the federal appeal was admissible.
Decisione estratta
The appeal was admissible; the office was entitled to challenge the cantonal judgment and the petition was properly signed.
Motivazione estratta
As the competent federal authority in migration matters, it could invoke a concrete federal-law dispute. No exclusion ground applied, and the signature requirement was met by the vice-director's signature.