In decision G 2/24 (25 September 2025), the Enlarged Board of Appeal confirmed its earlier ruling in G 3/04: a third party intervening during opposition appeal proceedings under Article 105 EPC cannot continue the proceedings once the sole appeal, or all appeals, have been withdrawn.
Under Article 105 EPC, a third-party facing infringement proceeding (or having initiated a non-infringement action following a cease-and-desist request) may intervene in pending opposition proceedings even after expiry of the 9-month opposition period.
An admissible intervention is treated as an opposition (Article 105(2) EPC). The intervener therefore acquires the status of an opponent and may raise all grounds of opposition, including new ones.
However, this position must be read in conjunction with Article 107 EPC, which governs appeals:
- Only a party to the first-instance proceedings adversely affected by the decision may file an appeal (Article 107, first sentence, EPC).
- Other parties may participate only as parties as of right (Article 107, second sentence, EPC).
Where intervention occurs at the appeal stage:
- the intervener was not a party to the first-instance proceedings;
- it therefore cannot qualify as an appellant under Article 107, first sentence, EPC;
- it joins the proceedings only as a party as of right under Article 107, second sentence, EPC.
This distinction is decisive. A party as of right may participate in the appeal, but does not control its existence.
No continuation without an appeal
Appeal proceedings before the EPO are governed by the principle of party disposition: they exist only as long as maintained by at least one appellant.
The Enlarged Board therefore confirmed that:
- if the sole appeal, or all appeals, are withdrawn, the appeal proceedings terminate in full;
- an intervener cannot take over or continue the appeal;
- this applies despite Article 105(2) EPC.
In short, Article 105 EPC allows entry into the proceedings, but does not confer an independent right to pursue an appeal under Article 107 EPC.
Practical implications
The decision is particularly relevant where parallel infringement or non-infringement actions are pending and an alleged infringer seeks central revocation before the EPO.
Intervention remains a powerful tool, notably allowing the introduction of fresh grounds of opposition. However, it is procedurally dependent on an existing appeal and cannot replace an independently maintained appeal.