The opposition procedure before the European Patent Office (EPO) is a post-grant, contentious,"(...) in G 9/91 and G 10/91 (...) the Enlarged Board held that in view of their special post-grant character, opposition proceedings under the EPC are in principle to be considered as contentious proceedings between parties normally representing opposing interests." in Decision G 9/93 (6 July 1994), Reasons for the Decision, item 1. inter partes, administrative"... the opposition procedure is a purely administrative procedure ..." in G 8/91, Reasons, point 7; "... the merely administrative character of the opposition procedure ..." in G 9/91, Reasons, point 18; and "Proceedings at this level are called "administrative" rather than "judicial" though it is difficult to see why – after all the opposition division is deciding a dispute between rival parties." in Jacob LJ, Unilin Beheer BV v Berry Floor NV & Ors EWCA Civ 364 (25 April 2007). procedure intended to allow any European patent to be centrally opposed. European patents granted by the EPO under the European Patent Convention (EPC) may be opposed by any person from the public (no commercial or other interest whatsoever need be shown). This happens often when some prior art was not found during the grant procedure, but was only known by third parties.
An opposition can only be based on a limited number of grounds,"The function of Article 100 EPC is to provide, within the framework of the EPC, a limited number of legal bases, ie a limited number of objections on which an opposition can be based." in Decision G 1/95 (19 July 1996), reasons 4.1. i.e. on the grounds that the subject-matter of the patent is not patentable, that the invention is insufficiently disclosed, or that the content of the patent extends beyond the content of the application as filed. The notice of opposition to a European patent must be filed in writing at the EPO (either at Munich, The Hague or Berlin), along with the payment of an opposition fee, within nine months from the publication of the mention of the grant of the patent in the European Patent Bulletin. Opposition Divisions of the EPO are responsible for the examination of oppositions. The opposition procedure may involve multiple opponents. According to the EPO, a European patent was once opposed by a record number of 27 opponents.European Commission Pharmaceutical Sector Inquiry, Preliminary Report - 28 November 2008, Comments from the EPO, 10.03.2009 (Final), page 5.
Purpose of the opposition proceedings, extent of the opposition, and available grounds for opposition The purpose of the EPO opposition proceedings is to give members of the public, such as competitors of the patent proprietor, the opportunity to challenge centrally before the EPO the validity of a granted European patent.G9/93, 6 July 1994, Reasons, point 3. No commercial or any other interest whatsoever need be shown. That is, the "opponent's motives are of no relevance for the purposes of the opposition procedure".T 84/19, reasons 5.3, citing "G 3/97, Reasons 3.2.2 and 3.2.3".
Opponents may challenge only some of the claims of the European patent (although this is in practice rather unusualDecision G 9/91 dated 31 March 1993, point 8.), therefore limiting the extent of the opposition to the challenged claims."By limiting the extent to which the patent is opposed to only certain subject-matters, the opponent deliberately refrains from making use of his right under the EPC to oppose remaining subject-matters covered by the patent. Such subject-matters are therefore, strictly speaking, not subject to any "opposition" in the sense of Articles 101 and 102 EPC, nor are there any "proceedings" in the sense of Articles 114 and 115 EPC in existence concerning such non-opposed subject-matters. Consequently, the EPO has no competence to deal with them at all." in Decision G 9/91 dated 31 March 1993, Reasons for the Decision, item 10.
However, an opposition can only be based on a limited number of grounds (i.e., objections) specified in the European Patent Convention, namely the grounds listed in . An opposition can be based on the grounds that the subject-matter of the patent is not patentable (Article 100(a) EPC, for instance because the claimed invention is not new or not inventive), on the ground that the invention is insufficiently disclosed to allow a person skilled in the art to carry it out (Article 100(b) EPC), or on the ground that the content of the patent extends beyond the content of the application as filed –"or, if the patent was granted on a divisional application or on a new application filed under , beyond the content of the earlier application as filed"– (Article 100(c) EPC). For example, an opposition cannot be validly based on the grounds that the invention lacks unity (), that the claims are not clear (), or that the right to the European patent does not belong to the proprietor of the patent ().
Filing and admissibility Before starting the substantive examination of the opposition, the Opposition Division examines whether the opposition must be considered as filed ("Is there an opposition?") and whether it is admissible ("Is the opposition admissible?"). The Opposition Division may find that the opposition is not deemed to have been filed, for instance because the opposition fee has not been paid within the nine-month opposition period, because the notice of opposition is not signed, or because the notice is not in an accepted language.
In order for an opposition to be admissible it must meet the provisions of , i.e. a notice of opposition must be filed by a natural or legal person within nine months from the publication of the mention of grant of the European patent in the European Patent Bulletin (the start of the nine-month opposition period depends on the publication of the mention of grant of the European patent in the European Patent Bulletin, not on the publication of the specification of the European patent Decision T 1644/10 (Versäumnis der Einspruchsfrist/UTISOL) of 26.10.2011, Catchword 1, Boards of Appeal of the EPO.), and , (formerly ) i.e. the notice of opposition must contain a statement of the extent to which the European patent is opposed and of the grounds on which the opposition is based, as well as an indication of the facts and evidence presented in support of these grounds.
In addition, an opposition is also rejected as inadmissible if it fails to meet the requirements of (formerly ) after the opponent was invited to remedy to these failures within a given time limit. If the opposition is not admissible, the opposition is rejected under . (formerly )
Inadmissible oppositions and oppositions which are deemed not to have been filed are not substantively examined (no examination on the merits). An opposition can only be rejected as inadmissible if the opposition has been first deemed to have been filed, and, if it is deemed to have been filed, the opposition exists, even if later the opposition is rejected as inadmissible. If an opposition is deemed not to have been filed, any opposition fee which has been paid is refunded.: "Deficiencies which may no longer be remedied, as a result of which the opposition is deemed not to have been filed". In contrast, if an opposition is rejected as inadmissible, an already paid opposition fee is not refunded.: "Deficiencies which may no longer be remedied in accordance with Rule 77(1) and (2), resulting in the opposition being rejected as inadmissible"; Visser, "The Annotated European Patent Convention", ed. 2009, p. 227 (Art. 99(1), point 4 "Procedure after filing".).
Straw man An opposition may be filed by a straw man to conceal the identity of the party actually interested in having the patent revoked. A strawman is "a party acting on behalf of another person." In 1999, the Enlarged Board of Appeal held that the use of a straw man did not render the opposition inadmissible unless "the involvement of the opponent is to be regarded as circumventing the law by abuse of process."Decision G 3/97 (Opposition on behalf of a third party) of 21 January 1999, Headnote 1(a), 1(b).
Filing of an opposition in common by a group of persons An opposition may be jointly filed by more than one natural or legal persons.: "Entitlement to oppose" Such an opposition is admissible upon payment of a single opposition fee.G 3/99 (Admissibility-joint opposition/appeal) of 18.2.2002, Headnote I. "An opposition filed in common by two or more persons, which otherwise meets the requirements of Article 99 EPC and Rules 1 and 55 EPC, is admissible on payment of only one opposition fee."; see also : "Payment of a single opposition fee". It must, however, be "clear throughout the procedure who belongs to the group of common opponents".G 3/99 (Admissibility-joint opposition/appeal) of 18.2.2002, Headnote III.
Substantive examination
If the opposition is admissible, the Opposition Division examines the grounds for opposition as to their merits. In that examination, the Opposition Division is not limited "to the facts, evidence and arguments provided by the parties and the relief sought" but it examines "the facts of its own motion". The Opposition Division may even, of its own motion, raise a new ground for opposition that the opponent(s) did not raise in their notice of opposition. The Opposition Division may do so "if there are clear reasons to believe that such grounds are relevant and would in whole or in part prejudice the maintenance of the European patent", the underlying aim being to avoid "the maintenance of European patents which are invalid".G 9/91, reasons 16. The patent proprietor also has the opportunity to reply to the grounds of opposition. That is, the proprietor may submit arguments and, to a certain extent, amendments in reply thereto.
Thus, in view of the grounds of opposition, and in view for instance of a prior art document introduced into the proceedings by the opponent, the proprietor may amend the patent, i.e. the description, claims, and drawings thereof, although amendments may not be filed as of right at any stage during the opposition proceedings.Decision T 383/11 of 17 April 2012, Reasons for the decision, 1.1. "The Boards of Appeal have derived, in particular from Rule 79(1) EPC, the principle that the proprietor does not have a right to have amendments admitted at any stage of opposition proceedings. At the discretion of the opposition division or the Board of Appeal, amendments can be refused if they are neither appropriate nor necessary (see case law of the Boards of Appeal, 6th edition 2010, VII.D.4.1.2, second paragraph)." The patent proprietor is master of its own patent in that the decision to amend or not, and how to amend the patent, is a decision of the proprietor alone (although the Opposition Division or the opponent may apply pressure to have amendments made).Decision T 1099/06, Reasons 6. The patent, however, may not be amended in such a manner that the amendment would lead to an extension of the protection conferred by the patent.