After withdrawal of an opposition, the opposition proceedings should be continued if they have reached such a stage that they are likely to result in a limitation or revocation of the European patent without further assistance from the opponent and without the opposition division itself having to undertake extensive investigations (T 197/88, OJ 1989, 412; see also the more recent decision T 36/11 and Guidelines D‑VII, 5.3 – November 2015 version). The continuation of the opposition proceedings under these circumstances follows from the EPO's general duty towards the public not to maintain patents which it is convinced are not legally valid at all or would be legally valid only with the necessary limitations (T 156/84, OJ 1988, 372; T 197/88).

In T 1668/08 the respondent (opponent) withdrew its opposition during the appeal proceedings and was hence no longer a party to those proceedings. The board decided to remit the case to the department of first instance for further prosecution. The board emphasised that during that further prosecution the opposition division would first need to decide, in accordance with R. 84(2) EPC, whether or not to continue the opposition proceedings of its own motion in view of the withdrawal of the opposition. It warned that its decision to remit should not be taken as indicative of the conclusion to be reached in this respect.

In T 36/11 the board held that an appeal by the patent proprietor against the decision of the opposition division to discontinue opposition proceedings after the withdrawal of the opposition was inadmissible because the patent proprietor had not been adversely affected by that decision.

In T 228/14 the opposition was withdrawn after the opposition division had delivered its decision in oral proceedings to revoke the patent. The board held that if the opposition proceedings had been terminated after the decision had been set aside, the patent would have stood as granted. But the proprietor had requested maintenance of the patent in amended form and thus no longer approved of the text of the patent as granted. The board stated that a decision to terminate the opposition proceedings would be contrary to the principle of party disposition as codified in Art. 113(2) EPC 1973.