Article 15

1. Without prejudice to Article 4, Member States whose laws authorise the registration of collective marks or of guarantee or certification marks may provide that such marks shall not be registered, or shall be revoked or declared invalid, on grounds additional to those specified in Articles 3 and 12 where the function of those marks so requires.

2. By way of derogation from Article 3(1)(c), Member States may provide that signs or indications which may serve, in trade, to designate the geographical origin of the goods or services may constitute collective, guarantee or certification marks. Such a mark does not entitle the proprietor to prohibit a third party from using in the course of trade such signs or indications, provided he uses them in accordance with honest practices in industrial or commercial matters; in particular, such a mark may not be invoked against a third party who is entitled to use a geographical name.