Opposition procedure before the European Patent Office
The opposition procedure before the European Patent Office (EPO) is a post-grant, contentious, inter partes, administrative 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, 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.
Purpose, framework, and available grounds
The purpose of the opposition proceedings is to give opponents, such as competitors, the opportunity to challenge the validity of a granted European patent. Opponents may also challenge only some of the claims of the European patent (although this is in practice rather unusual), therefore limiting the framework of the opposition to the challenged claims.
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 Article 100 EPC. 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 Article 61 EPC, beyond the content of the earlier application as filed"– (Article 100(c) EPC). An opposition can for instance not be validly based on the grounds that the invention lacks unity (Article 82 EPC) or that the right to the European patent does not belong to the proprietor of the patent (Article 60(1) EPC).
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
- Article 99(1) EPC, 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), and
- Rule 76(2)(c) EPC, 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 Rule 76(2)(a), (b) and (d) EPC 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 Rule 77(1) or (2) EPC.
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. In contrast, if an opposition is rejected as inadmissible, an already paid opposition fee is not refunded.
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."
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. Such an opposition is admissible upon payment of a single opposition fee. It must, however, be "clear throughout the procedure who belongs to the group of common opponents".
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". 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. 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). 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.
If amendments are made to the patent during the opposition proceedings, the patent (and the invention to which it relates) must meet the requirements of the EPC. These requirements notably include the requirements of support in the description and clarity (Article 84 EPC), even though those are not listed as grounds of opposition in Article 100 EPC.[notes 1] However, the requirements to be met by the amended patent do not include the requirement of unity of invention (because divisionals cannot be filed after grant).
During the opposition, oral proceedings may take place at the request of the EPO or at the request of any party to the proceedings, i.e. the patentee or an opponent. The oral proceedings are held before the Opposition Division itself. They are held in Munich, the Hague or Berlin, and are public unless very particular circumstances apply. This contrasts with oral proceedings held before an Examining Division, which are not public. The list of public oral proceedings in opposition before the EPO is available on its web site. The right to oral proceedings is a specific and codified part of the procedural right to be heard. A decision is generally pronounced at the end of the oral proceedings, with reasons to follow in writing.
Outcome and effects of the opposition
The opposition proceedings may have one of three outcomes:
- The patent is maintained as granted. This is the outcome if the opposition is rejected or if the Opposition Division decides to discontinue the opposition proceedings. The Opposition Division may decide to discontinue the opposition proceedings notably if the sole opposition or all the oppositions have been withdrawn and the patent proprietor is therefore the only remaining party to the proceedings. The withdrawal of an opposition may result from a settlement reached between the proprietor and the opponent. The opposition proceedings may also be discontinued "[i]f the European patent has been surrendered in all the designated Contracting States or has lapsed in all those States".
- The patent is maintained in an amended form. In this case, a new patent specification is published.
- The patent is revoked. This is the most successful outcome for the opponent, although the maintenance of a patent in an amended form may also be regarded as a success.
A decision of the EPO to revoke a European patent is final (when the opportunity to appeal before the EPO is exhausted), which makes the opposition proceedings at the EPO especially attractive for opponents. In contrast, a decision of the EPO not to revoke a European patent (the decision instead maintaining the patent as granted or in an amended form) leaves the way open for revocation by the national court. The EPO decision does not create an estoppel precluding a subsequent challenge by an unsuccessful opponent at the national level (at least before the English courts). The validity of a European patent can be scrutinised both at the national level, before a national court, and at the international level, before the European Patent Office during opposition. The same is not true for infringement proceedings, upon which national courts exercise exclusive jurisdiction.
Apportionment and fixing of costs
Each party to the opposition proceedings normally bears the costs it has incurred, unless the Opposition Division (or, in appeal proceedings, the Board of Appeal under Rule 100(1) EPC), for reasons of equity, orders a different apportionment of costs. For example, in case T 1306/05, a highly relevant document had been lately filed, without any valid justification, by the opponent during the oral proceedings before the Board of Appeal, thus rendering useless both the oral proceedings and the patent proprietor preparation thereto. A different apportionment of costs has been ordered by the Board of Appeal. The patent proprietor has requested, under Rule 88(2) EPC and Rule 100 EPC, about €26,000 to be paid by the opponent.
During first instance proceedings, a decision on apportionment of costs forms part of the main decision of the Opposition Division. The main decision however only deals with the obligation on the party or parties concerned to bear costs (apportionment), whereas the actual amounts to be paid by one party to another are dealt with in another decision, namely a decision on the award (fixing) of costs. A decision on the award of costs is taken only after a decision apportioning the costs has been taken and if a request is submitted to that effect. When a Board of Appeal has to rule on an apportionment of costs, both the apportionment of costs and the fixing of costs to be apportioned are dealt with in a single decision.
Transfer of opponent status
The opponent status cannot be freely transferred. As far as legal persons are concerned, the opposition can only be transferred or assigned to a third party together with the business assets belonging to a company, i.e. its economic activity, and more precisely the assets in the interests of which the opposition was filed. However, the status of an opponent passes to, i.e. is transmitted to, the opponent's universal successor in law in the case of a universal succession, such as for example in the case of a merger of two companies.
Intervention and observations by third parties
Intervention under Article 105 EPC
Under Article 105 EPC, any third party may intervene in ongoing opposition proceedings after the 9-month opposition period has expired, if the third party proves that "(a) proceedings for infringement of the same patent have been instituted against him, or (b) following a request of the proprietor of the patent to cease alleged infringement, the third party has instituted proceedings for a ruling that he is not infringing the patent." In other words, a third party may intervene "if faced with an infringement action or allegation of infringement (...) instituted in a national jurisdiction under national law."
The admissibility of an intervention is subject to conditions. The so-called notice of intervention must notably be filed within three months of the date on which proceedings referred to in Article 105 are instituted. An admissible intervention is treated as an opposition. If the intervention is admissible, the intervener becomes party to the opposition proceedings. An intervention may be based on any ground for opposition under Article 100 EPC, and the intervener may naturally also introduce new facts and arguments, which can therefore not be regarded as late filed.
The possibility to intervene not only exists during pending opposition proceedings before an Opposition Division (i.e., during the first instance proceedings), but also during subsequent pending appeal proceedings before a Board of Appeal (i.e., during the second instance proceedings). An intervener who intervened during appeal proceedings is, however, not treated as appellant, but merely as party as of right within the meaning of Article 107(second sentence) EPC. This has the consequence that, if the sole appellant withdraws their appeal, the appeal cannot continue with only an intervener who intervened during the appeal.
Observations by third parties under Article 115 EPC
Independently from the possibility to intervene in opposition proceedings (and then to become party to the proceedings), anyone may also file observations under Article 115 EPC. After publication of a European patent application, and a fortiori after grant of a European patent, anyone may file observations regarding the patentability of the invention which is the subject of the application (during examination proceedings) or patent (during opposition proceedings). In contrast to an intervener however, a person filing observations during opposition proceedings does not become party to the proceedings. This notably means that such person does not acquire the "bundle of procedural rights" created "in respect of the opponent", such as the right to be heard before any decision is taken. Observations by third parties, which must be filed in writing, may be filed by post or online. According to Board of Appeal 3.3.08, the observations have to be signed "in order to allow an identification of the third party" and, unless "adopted by a party to the proceedings as its own" or by the competent organ of the EPO of its own motion, "anonymous third party observations are to be disregarded altogether."
Statistics, costs and duration
Overall, about 5.5-6% of the European patents granted by the European Patent Office are opposed. Of those, over the course of 1980–2005, about 1/3 were revoked, 1/3 were maintained in an amended form, which generally means "reduced in scope", and 1/3 were maintained as granted, that is, the opposition was rejected. The same figures were cited in 2013. The opposition rate (i.e. the number of oppositions filed per 100 granted patents) before the EPO is consistently higher in the closest available proxy for the pharmaceutical sector than it is in organic chemistry and in all sectors (overall EPO average). The success rate depends however on the technical area (i.e., on the IPC classes).
The main reasons for revocation of a patent in opposition are a lack of inventive step (43%), a lack of novelty (22%) and an extension beyond the content of the application as filed (11%).
Filing an opposition before the EPO is reportedly relatively affordable, "as the cost varies between €6000 and €50,000 (including patent lawyers’ fees)" (as of 2009). In contrast, the costs for litigating a European patent can be much higher ("For example, in Germany the total litigation costs can be as high as €2 million with €10 million at stake"). An opposition case is reported to take on average three years to be handled by the EPO.
Parallel national proceedings
The "possibility of parallel validity proceedings in national courts and in the EPO is inherent in the legal arrangements in the EPC under which the EPO was established". If a third party files an opposition to a European patent with the EPO and also, in parallel, initiates a revocation action (also called "nullity action" or "validity proceedings") against the same patent before a national court, the national court (at least in England) may exercise its discretion to either
- stay the national proceedings, in order to wait the outcome of the EPO opposition proceedings, or
- allow the revocation proceedings to go ahead, without waiting the outcome of the EPO proceedings.
The rules and practice differ from country to country in that respect. "For example, as of 2008, Belgium and France will stay the main proceeding until a final decision has been reached by the EPO whereas in Germany, Italy, the Netherlands and in the United Kingdom such a stay is not automatic and in most cases the courts will continue the proceedings notwithstanding the opposition. ... However, in Germany national nullity proceedings cannot be started before the Federal Patent Court until the EPO opposition proceedings have been concluded or the opposition period has expired."
Composition of an Opposition Division
According to Article 19(2) EPC, "[a]n Opposition Division shall consist of three technically qualified examiners, at least two of whom shall not have taken part in the proceedings for grant of the patent to which the opposition relates. An examiner who has taken part in the proceedings for the grant of the European patent may not be the Chairman." Violations of Article 19(2) EPC are considered to be substantial procedural violations. If an Opposition Division considers it necessary in a particular case, the Opposition Division may be enlarged by the addition of a legally qualified examiner (who cannot "have taken part in the proceedings for grant of the patent").
The same principles should constrain the composition of a Board of Appeal in opposition appeal proceedings vs. its composition in examination appeal proceedings in relation respectively to a European patent and the European patent application that gave rise to that patent.
- See also decision T 936/04 of 24 April 2008 on whether the double patenting prohibition can be raised in opposition proceedings: "It is within the discretion of the instances of the EPO to raise the objection in opposition or opposition appeal proceedings against proposed amended claims, but this should be done only in clear cases" (catchword 1).
- "(...) 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.
- "... 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).
- T 22/09 (Party status/Fischer-Tropsch Catalysts/SASOL TECHNOLOGY), Reasons for the Decision, 2 (Technical Board of Appeal 3.3.07 of the European Patent Office 21 June 2013) ("Locus standi to oppose a European patent is defined in extremely broad terms. Under Article 99(1) EPC "any person" may file a notice of opposition within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin. The opponent does not have to have any special interest in challenging the patent: G 1/84 (OJ EPO 1985, 299) and T 798/93 (OJ EPO 1997, 363).").
- "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.
- Article 99(1) EPC
- Article 19(1) EPC
- European Commission Pharmaceutical Sector Inquiry, Preliminary Report - 28 November 2008, Comments from the EPO, 10.03.2009 (Final), page 5.
- G9/93, 6 July 1994, Reasons, point 3.
- Decision G 9/91 dated 31 March 1993, point 8.
- "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.
- Rule 3 EPC
- Rule 77(1) EPC
- (in German) Decision T 1644/10 (Versäumnis der Einspruchsfrist/UTISOL) of 26.10.2011, Catchword 1, Boards of Appeal of the EPO.
- Rule 76(2)(c) EPC (formerly Rule 55(c) EPC 1973)
- Rule 76(2)(a), (b) and (d) EPC (formerly Rule 55(a), (b) and (d) EPC 1973)
- Rule 77(1) or (2) EPC (formerly Rule 56(1) or (2) EPC 1973)
- Guidelines for Examination in the EPO, section d-iv, 1.4.1 : "Deficiencies which may no longer be remedied, as a result of which the opposition is deemed not to have been filed".
- Guidelines for Examination in the EPO, section d-iv, 1.4.2 : "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".).
- T 22/09 (Party status/Fischer-Tropsch Catalysts/SASOL TECHNOLOGY), Reasons for the Decision, 2 (Technical Board of Appeal 3.3.07 of the European Patent Office 21 June 2013) ("An opposition may be filed by a "straw man", that is to say a party acting on behalf of another person (...).").
- Decision G 3/97 (Opposition on behalf of a third party) of 21 January 1999, Headnote 1(a), 1(b).
- Guidelines for Examination in the EPO, section d-i, 4 : "Entitlement to oppose"
- 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 Legal Research Service for the Boards of Appeal, European Patent Office, Case Law of the Boards of Appeal of the EPO (9th edition, July 2019), iv.c.2.1.7.a : "Payment of a single opposition fee".
- G 3/99 (Admissibility-joint opposition/appeal) of 18.2.2002, Headnote III.
- Article 101(1) EPC
- Article 114(1) EPC
- G 9/91, reasons 16.
- Rule 80 EPC
- Rule 79(1) EPC
- 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)."
- Decision T 1099/06, Reasons 6.
- Article 123(3) EPC
- Article 101(3) EPC
- Decision G 9/91 of 31 March 1993, point 19 of the reasons: "(...) in case of amendments of the claims or other parts of a patent in the course of opposition or appeal proceedings, such amendments are to be fully examined as to their compatibility with the requirements of the EPC (...)".
- Decision G 1/91 of 9 December 1991. The reference to Article 102(3) in the decision is a reference to Article 102(3) EPC 1973, corresponding to Article 101(3)(a) EPC (of the revised text of the Convention, the so-called EPC 2000).
- Article 116(1) EPC
- Article 19(2)(fourth sentence) EPC
- Article 116(4) EPC
- Article 116(3) EPC
- EPO web site, Oral proceedings calendar. Consulted on 28 October 2012.
- Decision T 1012/03 of 1 December 2006, Reasons 25. "The right to oral proceedings according to Article 116 EPC is a specific and codified part of the procedural right to be heard according to Article 113(1) EPC."
- Guidelines for Examination in the EPO, section e-iii, 9 : "Delivery of the decision"
- Article 102(2) EPC
- See for instance decision T 36/11 of 30 January 2012, Reasons for the Decision, item 1.4. See also Rule 84(2) EPC (formerly Rule 60(2) EPC 1973) and Guidelines for Examination in the EPO, section d-vii, 5 : "Continuation of the opposition proceedings in the cases covered by Rule 84".
- van de Kuilen, Aalt (2013). "Successful European oppositions: Analysis for the patent information professional". World Patent Information. 35 (2): 126–129. doi:10.1016/j.wpi.2012.12.002.
- Rule 84(1) EPC
- Article 102(3) EPC
- Article 102(1), (4) and (5) EPC
- Article 106 EPC
- Malwina Mejer, Bruno van Pottelsberghe de la Potterie, "Economic Incongruities in the European Patent System"[permanent dead link], ECARES working paper 2009‐003, January 2009.
- Bossung, Otto. "The Return of European Patent Law in the European Union". IIC. 27 (3/1996). Archived from the original on 4 March 2012. Retrieved 30 June 2012.
(...) these courts [the courts of the EU Member States] cannot confirm a patent that an EPO appeal board has held to be unpatentable, or has revoked on opposition.
- Glaxo Group Ltd v Genentech Inc & Anor  EWCA Civ 23 (31 January 2008)
- Article 16 of the Rules of Procedure of the Boards of Appeal (RPBA)
- Article 104 EPC and Rule 88(1) EPC
- (in French) Decision T 1306/05 of 10 July 2008, Boards of Appeal of the EPO.
- (in French) Laurent Teyssedre, T1306/05 : répartition des frais, Le blog du droit européen des brevets, 19 October 2008. Consulted on 8 November 2008.
- Guidelines for Examination in the EPO, section d-ix, 1.2 : "Decisions on the apportionment of costs".
- Rule 88(2) EPC
- Legal Research Service for the Boards of Appeal, European Patent Office, Case Law of the Boards of Appeal of the EPO (9th edition, July 2019), iii.r.3.2 : "Procedure for fixing costs", third paragraph: "Where the boards of appeal have to rule on the apportionment of costs, they have the power (...) not only to apportion but also to fix the costs (...)." See for example T 1663/13 of 14 July 2016.
- Decision G 2/04 of 25 May 2005, Headnote I.(a).
- Decision T 0384/08 of 26 June 2009, Reasons 24.
- Beck, Michaël (2017). "Conflicts of Laws in Proceedings Before the European Patent Office". IIC. 48 (8): 925–952. doi:10.1007/s40319-017-0643-5. hdl:10067/1470880151162165141. ISSN 0018-9855.
... the Boards of Appeal have recognized the transfer of opponent status as an accessory of the assets of the business division in whose interest the opposition was lodged, the transfer of which is governed by national law, and as a result of a universal succession.
- G 4/88, OJ EPO 1989, 468, point 4 of the Reasons; see also Decision T 518/10 of 9 April 2013, point 3.1 of the Reasons.
- Article 105(1) EPC. Regarding the need for ongoing opposition proceedings for an intervention to be admissible, see for example "(...) opposition proceedings before the EPO cannot be "reopened" due to the advent of an intervener (...)" in Decision T 1713/11 of 12 December 2012, reasons 2.7.
- Decision T 1713/11 of 12 December 2012, reasons 2.2.
- Rule 89 EPC
- Rule 89(1) EPC
- Article 105(2) EPC
- Decision G 1/94 (OJ 1994, 787), headnote; and decision T 1235/14 of 10 October 2018, point 3.
- Decision G 1/94 (OJ 1994, 787), point 10.
- Decision G 3/04.
- Article 115 EPC
- G4/88, 24 April 1989, Reasons, point 2.
- Rule 114 EPC
- Decision of the President of the European Patent Office dated 10 May 2011 concerning the filing of third party observations under Article 115 EPC by means of an online form, EPO Official Journal 7/2011, p. 418; Notice from the European Patent Office dated 10 May 2011 concerning the filing of third party observations under Article 115 EPC by means of an online form, EPO OJ 7/2011, p. 420.
- Decision T 146/07 dated 13 December 2011, Reasons for the Decision, 3 to 6, citing Schachenmann in: Singer/Stauder, Europäisches Patentübereinkommen, 5th ed., Art. 115 marg. no. 13
- EPO web site, CA/PL 29/99 dated 8.11.1999, Revision of the EPC: limitation procedure, in Travaux préparatoires 1997-2000, Patent Law Committee documents, item II.7.
- European Commission, Pharmaceutical Sector Inquiry, Preliminary Report (DG Competition Staff Working Paper), 28 November 2008, pages 10-11 (pdf, 1.95 MB).
- See for instance Decision T 1349/10 (Composition of Opposition Division/ETHICON) of 2 February 2011, Reasons 4, citing also decisions T 251/88, T 939/91, T 382/92, T 476/95, and T 838/02.
- T 1028/96 (Suspected partiality/DU PONT DE NEMOURS) of 15.9.1999, reasons 6.6: "Article 19(2) EPC requires i.a. that an examiner who has taken part in the proceedings for the grant of the European patent shall not be the chairman of the Opposition Division. The Board does have some sympathy for the respondents' argument that, in the circumstances set out above, such prohibition should apply all the more to the second instance in view of its judicial function at supreme level within the European patent system. (...)" See also T 1889/13 of 20.5.2015, reasons 2.4.1 and 2.4.2.
- European Patent Convention, Part V, Opposition and Limitation Procedure (Art. 99 to 105)
- Guidelines for Examination in the EPO, section d : Guidelines for Opposition and Limitation/Revocation Procedures
- Legal Research Service for the Boards of Appeal, European Patent Office, Case Law of the Boards of Appeal of the EPO (9th edition, July 2019), iv.c : "Opposition procedure"
- Special edition 1/2010, Ancillary Regulations to the European Patent Convention (PDF, 1.9 MB), section d.4: "Opposition" (pp. 73–74).
- Notice from the EPO concerning the opposition procedure as from 1 July 2016, Official Journal 2016, A42