In G 9/91 and G 10/91 (OJ 1993, 408 and 420) the Enlarged Board held that R. 76(2)(c) EPC (R. 55(c) EPC 1973) made sense only when interpreted as having the double function of governing (together with other provisions) the admissibility of the opposition and of simultaneously establishing the legal and factual framework within which the substantive examination of the opposition was in principle to be conducted.

The legal framework of an opposition case is defined solely by (i) the extent to which the patent is actually opposed and (ii) the grounds upon which it is opposed, whilst its factual framework is determined by the facts, evidence and arguments adduced and set out in the notice of opposition pursuant to R. 76(2)(c) EPC (T 737/92; see also T 1900/07 with regard to the legal framework). A distinction has to be made between the two main requirements of R. 76(2)(c) EPC, i.e. the indication of the extent to which the European patent is opposed and the grounds for opposition.