In T 830/03 the opposition division had issued a second written decision intended to supersede a first written decision already sent. The board noted that the need for legal certainty required a presumption of validity in favour of a written decision which was notified to the parties by an opposition division in accordance with the formal requirements of the EPC 1973, in particular R. 68 to R. 70 EPC 1973 (now R. 111 to 113 EPC). Once the decision was pronounced and the (first) written decision, in the case at issue, notified to the parties, the opposition division was bound by it even if it considered its decision not to "have any legal effect" (see T 371/92, OJ 1995, 324). The decision could be set aside only by the second instance on the condition that an allowable appeal was filed under Art. 106 EPC 1973. With the filing of the first notice of appeal, the power to deal with the issues involved in this case passed from the department of first instance to the appeal instance (devolutive effect of the appeal). All actions carried out by the opposition division after the notification of the (first) decision, and a fortiori after the filing of the first appeal, were ultra vires and thus had no legal effect.
In T 1257/08 the board, referring to T 830/03 stated that under the presumption of legal validity, the first written decision notified constitute the opposition division's only legally valid written decision. The opposition division was bound by it and could not itself set it aside. Furthermore, only the first written decision as legally valid decision was appealable.
The board in T 1093/05 (OJ 2008, 430) pointed out that it is established board of appeal and Enlarged Board of Appeal case law that an examining division is bound by its final decision on an application, which can be set aside only following an admissible, allowable appeal (see G 12/91, OJ 1994, 285; G 4/91, OJ 1993, 707; T 371/92, OJ 1995, 324; T 1081/02; T 830/03). In view of this established case law, the board could not subscribe to the view expressed in T 971/06 that an erroneous decision is a nullity and therefore no appeal needs to be filed against it. (NB Only one decision was issued in T 971/06).