The effects of this vary, depending on whether the opponent in the appeal proceedings is the appellant or the respondent.
In G 8/93 (OJ 1994, 887) the Enlarged Board held that if the opponent as sole appellant filed a statement withdrawing his opposition this immediately and automatically terminated the appeal proceedings, irrespective of the patentee's consent. The proceedings were also terminated if in the board's view the requirements under the Convention for maintaining the patent were not met. The Enlarged Board emphasised the distinction between the power to initiate and continue proceedings and the power to clarify the facts in pending proceedings. According to its case law, in appeal proceedings the former was exclusively the province of the appellant, whereas the latter might be exercised by the board subject to Art. 114 EPC 1973 provided proceedings were pending.
This confirmed the earlier case law (see T 117/86, OJ 1989, 401; T 129/88, OJ 1993, 598; T 323/89, OJ 1992, 169; T 381/89 and T 678/90). Any statements made following withdrawal of the opposition are irrelevant (see T 381/89). T 544/89 is overruled.
If, however, the opponent is the respondent, withdrawal of the opposition does not affect the appeal proceedings (see e.g. T 135/86, T 362/86, T 373/87, T 194/90, T 629/90, OJ 1992, 654; T 138/91, T 329/92, T 627/92, T 463/93, T 798/93 (OJ 1997, 363), T 78/95, T 4/04 and T 340/05). The board therefore has to reexamine the substance of the opposition division's decision. However, it could set it aside and maintain the patent as requested by the appellant only if the specification meets the requirements of the EPC. When the board examines the decision, evidence can be cited which has been submitted by an opponent before the opposition was withdrawn (T 340/05, see also T 900/03). However, under T 789/89 (OJ 1994, 482) withdrawal of an opposition by the respondent means the respondent ceases to be party to the appeal proceedings in respect of the substantive issues; he remains party to them only as regards apportionment of costs (confirmed by T 82/92, T 884/91, T 329/92 and T 340/05). T 484/89 on the other hand found that the respondent remained party to the proceedings although not obliged to take an active part. The opposition division's decision is not examined "by the Office of its own motion", but as a result of the appeal, i.e. on the basis of the "request" by the appellant for the contested decision to be revoked (T 958/92).
For the consequences of withdrawal of the opposition as regards the board's powers of ex officio examination of the facts, see below Chapter IV.E.3.4 "Facts under examination".