In G 3/04 the Enlarged Board ruled that an intervener, if the appeal is filed by someone other than him, is a party as of right according to Art. 107, second sentence, EPC. If the intervention is filed during the appeal proceedings, the intervener, again because he can only acquire the status of an opponent, has the same rights and obligations – apart from the right to raise new grounds of opposition – as any opponent who has not filed an appeal. If in this case the sole, or each, appeal has been withdrawn, the appeal proceedings are terminated in respect of all the substantive issues, including the new grounds for opposition raised by the intervener, for all the parties (see also T 694/01, OJ 2003, 250).
In G 1/94 (see in this chapter III.P.1.4.2), the Enlarged Board also examined the question of whether an intervener during appeal proceedings could raise any of the grounds for opposition under Art. 100 EPC 1973 even if they had not yet been examined by the opposition division, and found in the affirmative. If a fresh ground for opposition was raised, the case should be remitted to the department of first instance unless the patent proprietor wished the board to rule on it there and then. In T 694/01 (OJ 2003, 250), it was made clear that where a board has decided to maintain a patent on the basis of a given set of claims and a description to be added to them, in subsequent appeal proceedings confined to the issue of the adaptation of the description the previous decision is res judicata and the intervener cannot therefore challenge this decision by introducing a new ground of opposition.