According to Article 107(1) of the Treaty, any aid granted by a Member State or through State resources in any form whatsoever which distorts or threatens to distort competition by favouring certain undertakings or the provision of certain goods shall be incompatible with the internal market, in so far as it affects trade between Member States.
Cependant, les autorités espagnoles ont expliqué que la municipalité de Madrid ne pouvait pas procéder à une telle modification motu proprio, et qu'elle devait proposer la modification du PGOU à la Communauté de Madrid.