In T 263/05 (OJ 2008, 329) the board had to consider the question of whether R. 29(2) EPC 1973 (R. 43(2) EPC) applied in opposition proceedings by virtue of the reference in R. 61a EPC 1973, as had been held by the opposition division.
To answer this question, the board reviewed decision G 1/91 (OJ 1992, 253), which had considered the effect of R. 61a EPC 1973 in the context of the requirement of unity. The Enlarged Board of Appeal had taken the view that the reference to Chapter II was only a general one and that R. 61a EPC 1973 could only be taken to refer "to those requirements which would still be reasonable to demand of the new documents relating to the amended patent". The purpose of opposition proceedings was to enable a party to oppose unjustified protective rights. The board concluded that R. 29(2) EPC 1973 did not apply in opposition proceedings to prohibit an amendment to a granted patent if it would be unreasonable to demand of the amended claims that they comply with this rule. This condition was satisfied in a case where otherwise R. 29(2) EPC 1973 would force the proprietor to abandon potentially valid subject matter already contained in the granted claims.
The board stated that it could not envisage any circumstances in which R. 29(2) EPC 1973 would be of any application in opposition proceedings. Once an amendment to the claims had been established to be necessary and appropriate having regard to the grounds of opposition, it would be unreasonable to impose the additional requirement that the amendment complied with the purely administrative provisions of R. 29(2) EPC 1973 (see also T 987/05, T 1242/06, OJ 2013, 42 and T 85/08).