The measure in question in that case was a partial exemption from excise duty on the diesel used for the heating of greenhouses.
Arrêt de la Cour de justice du 15 novembre 2011, Commission et Espagne/Government of Gibraltar et Royaume-Uni, affaires jointes C-106/09 P et C-107/09 P, ECLI:EU:C:2011:732, points 101 et suivants.