1. An action or a counterclaim for a declaration of invalidity of a Community design may only be based on the grounds for invalidity mentioned in Article 25.
2. In the cases referred to in Article 25(2), (3), (4) and (5) the action or the counterclaim may be brought solely by the person entitled under those provisions.
3. If the counterclaim is brought in a legal action to which the right holder of the Community design is not already a party, he shall be informed thereof and may be joined as a party to the action in accordance with the conditions set out in the law of the Member State where the court is situated.
4. The validity of a Community design may not be put in issue in an action for a declaration of non-infringement.