In T 752/93 of 16 July 1996 date: 1996-07-16, T 637/96, and T 1002/95 the opposition division had maintained the patent in amended form and only the opponent had appealed. The non-appealing patentee proposed amendments during the appeal proceedings. In T 752/93 date: 1996-07-16 and T 1002/95 the board found that amendments proposed by a non-appealing patentee could, according to G 9/92 date: 1994-07-14 (OJ 1994, 875), be rejected as inadmissible by the board of appeal if they were neither appropriate nor necessary, i.e. had not been occasioned by the appeal. According to T 752/93 date: 1996-07-16 the patentee should therefore have the opportunity to correct erroneous amendments if these were detected later in the proceedings. Similarly, in T 637/96, the respondent (patentee) was able to request restoration of the claim as granted, as the amendment made to it in opposition proceedings did not change its subject-matter (i.e. the claim as granted and amended meant the same thing) and was therefore unnecessary. In T 752/93 date: 1996-07-16 and T 637/96 the amendments were found not to worsen the sole appellant's position and the board thus considered them appropriate and necessary. In T 1002/95 the board pointed out that under R. 57a EPC 1973, which came into force after decisions G 9/92 date: 1994-07-14 and G 4/93, a patentee was entitled to make "appropriate and necessary" amendments occasioned by grounds for opposition specified in Art. 100 EPC 1973, even if the respective ground was not invoked by the opponent.

In T 23/04 the board made it clear that the requirements of reformatio in peius do not imply any right of the appealing party (opponent) to dictate the form any proposed amendments may take, and certainly to prescribe a form of amendment which would be maximally disadvantageous to the patent proprietor.

In T 1380/04 the board, referring to G 1/99 (OJ 2001, 381), held that the deletion of a term by the patentee/respondent could not be allowed, as this would have worsened the legal position of the appellant, contrary to the prohibition of reformatio in peius. It was immaterial that the term had only been introduced at the suggestion of the opposition division, as this did not alter the fact that approval of this amendment was the responsibility of the proprietor.

However, if the opponent and sole appellant deliberately refrains from invoking the prohibition of reformatio in peius against a claim request submitted by the respondent (patentee) which extended the scope beyond that of the claims as maintained by the department of first instance, the board need not apply the principle of the prohibition of reformatio in peius of its own motion. Following the principle of party disposition, any right protecting an appellant against an outcome that puts it in a worse position than if it had not appealed, may be waived (T 1544/07).

The board observed in T 111/10 that the exceptional possibilities for amendment foreseen by G 1/99 in application of the principle of the prohibition of reformatio in peius only applied if the patent would otherwise have to be revoked, i.e. the patent proprietor (respondent) did not have any other possibility of amendment which would allow rescue of even part of the opposed patent. In the case at issue, however, such a possibility existed. Although this would have resulted in a restriction of scope, it could not be considered unduly inequitable for a patent proprietor who, not having appealed, could not from the outset expect to get more than what was already maintained by the opposition division.