3.1 Basic principles 

The European patent as granted or as amended in opposition, limitation or revocation proceedings determines retroactively the protection conferred by the European patent application.

Opposition proceedings will frequently give rise to amendments to the claims, following from grounds for opposition raised under Art. 100. Reasoned requests filed independently by proprietors of the patent for an amendment to the claims, e.g. for limitation of the patent in view of an aspect of the state of the art which has come to their knowledge, may also result in amendments to the claims after examination by the opposition division.

In such cases the claims of the European patent may not be amended in such a way as to extend the protection conferred by the patent.

Art. 123(3) is directly aimed at protecting the interests of third parties by prohibiting any broadening of the claims of a granted patent, even if there is a basis for such broadening in the application as filed (see G 1/93, Reasons 9).