In T 446/95, in which an infringement action had been based on a French national patent, the board held that the intention and purpose of an intervention in accordance with Art. 105 EPC 1973 was to enable the assumed infringer to defend himself against the action by the patentee based on the opposed European patent, in order to prevent the EPO and the national courts handing down contradictory decisions on the validity of European patents. In the case in question, the fact that the European patent had claimed priority from the French patent and that France had been designated was irrelevant, as there was no legal basis for intervening in the European patent on the basis of an infringement action relating to the French patent. The admissibility of an intervention before the EPO could not depend on a provision of national law. The intervention was therefore inadmissible.

In T 7/07 the board held that the patent in suit was not granted for Lithuania under the EPC, as Lithuania was an extension state and therefore could not be designated for a European patent. The national law of the extension state governs the extension proceedings and the legal effects of the extension. The infringement proceedings were based on a patent which had been granted for a number of EPC contracting states and which, under Lithuanian law, also took effect in Lithuania, but exclusively on the basis of Lithuanian national law, which conferred the same effect on this patent as on a national patent. As a result, the infringement proceedings were not based on the European patent in suit in the opposition proceedings. The board agreed with the findings in T 1196/08 that an intervention based on proceedings for infringement of a patent that has effect in a particular state solely on the basis of national law is inadmissible because it fails to meet one of the requirements under Art. 105(1)(a) EPC. It therefore regarded the intervener's submissions as third-party observations under Art. 115 EPC.