132The determination of the set of undertakings which are in a comparable factual and legal situation depends on the prior definition of the legal regime in the light of whose objective it must, as the case may be, be examined whether the factual and legal situation of the undertakings favoured by the measure in question is comparable with that of those which are not (judgment of 21 December 2016, Commission v Hansestadt Lübeck, C‑524/14 P, EU:C:2016:971, paragraph 60).