On 25 March 2010, the European Court of Justice (ECJ) ruled on the use of a third party’s trade mark as a key word within Google Ad Words, a service that allows posting sponsored links which are displayed along with search results. Referring to some previous case law, including the well known Google France case, the ECJ held that the proprietor of a trade mark can prohibit such use by a third party only to the extent that the use affects or is liable to adversely affect the functions of the trade mark as indicator of origin. Particularly, use by the advertiser is unlawful in the case where the ad does not enable an average internet user, or enables that user only with difficulty, to ascertain whether the goods or services referred to therein originate from the proprietor of the trade mark or an undertaking economically connected to it or, on the contrary, originate from a third party.