In some cases the conflict between Art. 123(2) and Art. 123(3) EPC 1973 can be resolved. In T 166/90 the board allowed an inadmissible feature in a granted claim to be replaced by other disclosed features, since this did not extend the scope of protection. The invention concerned an opaque plastic film. The product claim as granted contained a feature stating that the density of the film was less than the arithmetical density from the type and proportion of the individual components. In opposition proceedings the patent proprietor claimed a process for manufacturing the film, but without including in his process claim the density-related feature. The board examined whether this would broaden the scope of the patent, asking if the process claim features which replaced the deleted feature necessarily limited the claim to films - like that in the granted product claim - with a density less than the arithmetical one. The board concluded that, with a probability bordering on certainty, the process now claimed would produce an opaque film of a density less than that arithmetically derivable from the type and proportion of its individual components. Thus, deleting the density-related feature had not in fact extended the scope of protection.
Decisions T 673/89 and T 214/91 followed T 271/84 (OJ 1987, 405), T 371/88 (OJ 1992, 157) and T 438/98, in ruling that amending a claim to remove an inconsistency did not contravene Art. 123(2) or Art. 123(3) EPC 1973 if the claim as corrected had the same meaning as the correct interpretation of the uncorrected claim in the light of the description. For another case concerning the conflict between Art. 123(2) and (3) EPC, see T 1202/07, which refers to T 1018/02 (extent of protection conferred by a claim feature not consistent with the description). The latter decision dealt in detail with interpretation of claims and can thus be distinguished from, in particular, T 438/98 (correction of an obvious clerical error).
In T 553/99 the board stated that if a claim as granted contained an undisclosed, limiting feature in contravention of Art. 123(2) EPC 1973 it could be maintained in the claim without violating Art. 123(2) EPC 1973 provided that a further limiting feature was added to the claim which further feature was properly disclosed in the application as filed, and deprived the undisclosed feature of all technical contribution to the subject-matter of the claimed invention.
With regard to the approach applicable in a case concerning the relationship between Art. 123(2) and Art. 123(3) EPC 1973, T 942/01 held it to be a principle in patent law (see for example G 1/93, OJ 1994, 541) that a patent could not be maintained unamended in opposition procedure if a violation of Art. 123(2) EPC 1973 had occurred during the examination procedure. In the case in point the respondents, during the opposition procedure, had correctly objected under Art. 123(2) EPC 1973 to the deletion of the feature in question, and the appellant had consequently reacted by cancelling the deletion, i.e. by reintroducing the deleted feature into claim 1. Such a cancellation of unallowable amendments during the opposition proceedings was normally possible under the provisions of the Convention, except where the unallowable amendment was a "limiting extension", so that its cancellation would extend the protection conferred by the patent and therefore contravene the requirements of Art. 123(3) EPC 1973 (G 1/93). According to the board, such a situation was the basis for T 1149/97 which had been cited by the respondents. However, that decision did not apply to the case at issue (T 942/01), which dealt with an unallowable extension only.
For an example of a "limiting extension" adding subject-matter contrary to Art. 123(2) EPC but at the same time limiting the scope of protection vis-à-vis what could have been claimed, so that its removal infringed Art. 123(3) EPC, see T 567/08.
Following the principles set out in G 1/93, the board came to the conclusion that in T 250/05 the patent could not be maintained unamended and that the patent could only be maintained if there was a basis in the application as filed for replacing such subject-matter without violating Art. 123(3) EPC. The sixth auxiliary request (which contained only one claim) met both prerequisites.
Furthermore, on the conflict between Art. 123(2) and (3) EPC, the appellant in T 195/09 referred to T 108/91 (headnote and points 2.2, 2.3 of the Reasons). The board pointed out that this decision had been clearly overruled by G 1/93 (on T 108/91, see also T 1202/07). The patent according to the auxiliary request contravened the requirements of Art. 123(3) EPC. The patent was revoked.