G 2/24 in a nutshell: EBoA clarifies intervener status in EPC appeals

In decision G 2/24, the EPO’s Enlarged Board of Appeal (EBoA) sheds light on the procedural status of an intervener in European Patent Convention (EPC) appeal proceedings.

In the underlying opposition appeal proceedings (T 1286/23), a third party unsuccessfully attempted to join the opposition proceedings at first instance but did so admissibly in the appeal proceedings.

After the sole appellant withdrew the appeal, the proceedings should have been terminated. It is current case law that an intervener cannot acquire an independent appellant party status under Article 107, first sentence, of the EPC but only be considered as a dependent party “as of right” according to the article’s second sentence. Therefore, after the withdrawal, the intervener cannot continue the proceedings on its own motion (see G 3/04).

The competent board of appeal (BoA), however, questioned this practice. It deemed that, since the role of an intervener in EPC appeal proceedings is not unambiguously set by the legal framework, and considering the intervener’s special procedural status, the intervener should be granted an independent party status during appeal and thus the right to continue the proceedings on its own initiative.

The BoA accordingly referred the following questions to the EBoA:

• “After withdrawal of all appeals, may the proceedings be continued with a third party who intervened during the appeal proceedings?”

• “In particular, may the third party acquire an appellant status corresponding to the status of a person entitled to appeal within the meaning of Article 107, first sentence, EPC?”

In its ruling on September 25 2025, the EBoA held the referral generally admissible as it concerns an aspect of fundamental importance for determining the third party's legal status and associated rights in appeal proceedings (see G 2/24, No. 7).

With regard to the BoA’s intention to deviate from G 3/04, however, the EBoA emphasised that it “does not find the prospect of a board of appeal referring a question of law solely because it disagrees with an earlier G-decision or opinion to be particularly appealing in terms of safeguarding consistent case law” (see G 2/24, No. 9).

To address the referred questions, the EBoA first examined the relevant legal background, including:

• Potential changes in the legal situation;

• The general legal concept of appeal proceedings;

• The requirements for qualification as a party in such proceedings; and

• The legal concept of interventions.

The decision G 3/04 had been issued before the EPC 2000 came into force, and the EBoA accordingly reviewed all amendments to the relevant articles (articles 99(1), 105, and 107, EPC) and their interpretation in conjunction with each other.

In conclusion, none of the EPC provisions relevant to the referral were found to be amended in a substantive manner after the decision G 3/04 was issued.

The EBoA explored the general legal concept of EPC appeal proceedings and highlighted that they are not foreseen as a continuation of the first-instance proceedings but serve only as a remedy to eliminate adverse effects of first-instance decisions.

In particular, the EBoA emphasised that the appeal is not an ex officio procedure, but the procedural scope is determined only by the decision under appeal, the appellant’s requests, and potential submissions of other parties in reply to the appellant’s grounds of appeal. Consequently, it depends only on the appellant initiating, determining the scope of, and concluding the procedure within its party’s power of disposal.

The EBoA held that party status under Article 107, first sentence, of the EPC can only be granted to parties that formally participated in the proceedings before the instance that issued the contested decision. Consequently, a third party that has not been admitted as a party to the first-instance proceedings is not entitled to appeal, unless the entitlement to participate was ignored due to a procedural error or incorrect application of the law.

Furthermore, the parties must be adversely affected by the decision, which is acknowledged when it fails to meet that party’s procedural requests. Any other “negative” or “disadvantageous” effect on a third party that has not formally participated in the first-instance proceedings does not fulfil the legal threshold required by Article 107, first sentence, of the EPC.

The EBoA elaborated that the only legal instrument for a third party to challenge a European patent under the EPC is filing an opposition according to Article 99 of the convention. The intervention, on the other hand, establishes a special legal framework that, due to its exceptional nature, inherently precludes an extensive interpretation and application.

The intervention is intended to provide third parties, after the opposition period, with the opportunity to examine the validity of a European patent that they are alleged to infringe. Interveners are therefore granted a fully fledged party status during opposition proceedings, as explicitly acknowledged in Article 105(2) of the EPC. They are, for example, not bound to any grounds for opposition presented by other parties. Still, the intervention is to be considered an accessory to the regular opposition proceedings, as it requires pendency of the opposition.

After analysing the relevant underlying legal concepts, the EBoA addressed the question about the party status of an intervener at appeal proceedings under the EPC and compared the findings with regulations in other jurisdictions.

The EBoA initially referred to G 1/94, wherein it was acknowledged that ambiguity remains as to the interpretation of Article 105 of the EPC in respect of intervention in appeal proceedings.

However, despite the benefits an intervener enjoys during opposition proceedings, which also apply to appeal proceedings (e.g., with regard to the liberty to present new grounds for opposition), the EBoA held that the party status during appeal proceedings is still only that of a party according to Article 107, second sentence, of the EPC; i.e., that of an opponent that did not appeal.

The EBoA highlighted that, in appeal proceedings, the principle of party deposition, together with the binding nature of the parties’ requests, defines the limits of any procedural action of all those involved in appeal proceedings; i.e., appellants, respondents, parties as of right, and the boards of appeal.

From this principle, it not only follows that the parties determine the start of the proceedings and their scope by their requests but also that “a board of appeal, as a matter of principle, may neither initiate nor continue appeal proceedings ex officio without a request from a party if the procedural act which gave rise to the proceedings has been withdrawn, unless procedural law permits continuation”.

And while an intervener at appeal enjoys the exception of not being bound to previously presented grounds for opposition, this exception neither changes its (dependent) party status nor the underlying principle of party disposition for appeal proceedings. No specific legal provisions to the contrary are apparent in the EPC that would justify a different interpretation. In particular, since the intervener at appeal was not a party of the first-instance proceedings, it cannot procedurally benefit from any status in the preceding opposition proceedings.

In conclusion, the EBoA found that the above-noted procedural limits do not allow for an expansive interpretation and application of Article 105(2) of the EPC mutatis mutandis or even by analogy, as was suggested by the BoA.

Consequently, if the sole appeal or all appeals are withdrawn, the appeal proceedings end with regard to all substantive issues for all parties involved (see G 2/24, No. 66).

The EBoA also did not find a single decision deviating from G 3/04.

In addition, to ensure harmonised application of the EPC and proceedings before national courts and authorities, the EBoA analysed the legal situation of interventions in several jurisdictions (Switzerland, Germany, France, the Netherlands, the UK, and the Unified Patent Court) and summarised that “[i]n the absence of a specific statutory provision stating that an intervention is independent of the main parties' procedural actions, an intervention is considered an accessory to the proceedings and ceases to have effect if the proceedings are terminated by the main parties.”.

The EBoA concluded that an intervention under the EPC is procedurally an accessory to the appeal proceedings initiated by one or more parties adversely affected by the decision under appeal (see G 2/24, No. 103).

The intervener in the appeal proceedings does not acquire an appellant status corresponding to the status of a party entitled to appeal within the meaning of Article 107, first sentence, of the EPC but is a party as of right according to the article’s second sentence (see G 2/24, No. 104). After withdrawal of the sole appeal or all appeals, the appeal proceedings cannot be continued with an intervener at appeal (see G 2/24, No. 105).

Consequently, the EBoA answered the referred questions in the negative.