Appeal proceedings before the Paris Court of Appeal following a patent opposition decision – the admissibility of new auxiliary claims is not self-evident

Statement of the facts

The decision of the Director General of INPI had maintained the patent in amended form, as per the first auxiliary request submitted by the patentholder.

During the appeal proceedings, the opposing company and appellant, which had requested that the decision be revoked, submitted thirteen prior art documents in support of its arguments aimed at proving that the subject matter of the patent lacked novelty or did not involve any inventive step. None of these documents had been submitted during the opposition proceedings themselves.

The admissibility of such documents may seem questionable to companies and attorneys familiar with opposition proceedings before the European Patent Office, in which the possibilities for a party to submit new evidence are very limited. However, such documents are admissible before the Court of Appeal because, under the terms of Article R. 411-38 of the French Intellectual Property Code, first paragraph:

In order to justify the pretensions they submitted to the Director General of INPI before the Court of Appeal hearing an appeal [against a patent opposition decision], the parties may invoke new arguments, produce new documents, or propose new evidence.

Naturally, the patentholder submitted two new auxiliary requests, limiting the claims in order to further distinguish the invention from the newly cited documents. However, the Court declared these new requests inadmissible, considering them to be new pretensions which, as indicated in the second paragraph of article R. 411-38, may only be submitted “to allow a ruling on issues arising from the intervention of a third party or the occurrence or disclosure of a fact.”

One could have expected that the opponent citing a dozen documents that had not been discussed at all before INPI would constitute a new fact justifying such a pretension. However, the Court ruled that “the newly submitted documents cannot be considered new facts, since they existed prior to the patent application and could have been taken into account at the time the patent was drafted.”

The new requests filed by the patentholder were therefore declared inadmissible, contrary to the opinion of the Director General of INPI, who considered that the inadmissibility of these requests would be unequitable to the patent owner. The patent was maintained in amended form according to a second auxiliary request which had already been submitted by the owner during the proceedings before INPI.

The Court therefore confirmed its ruling of 9 April 2025, in which it had stated that newly submitted auxiliary requests during appeal proceedings were inadmissible. In that case, however, the opponent had not invoked documents not previously submitted to INPI.

What lessons can be learned from this ruling?

We find the Court's position regrettable.

Firstly, it creates a clear inequality between the parties by not providing patentholders with the opportunity to defend themselves against challenges to the patentability of the protected invention, said challenges relying on prior art documents not known to the patentholder, and firstly presented by the opponent during appeal proceedings.

The idea that a patentholder could have been aware of all the prior art that could be used to oppose their patent at the time of its drafting is very difficult to sustain for attorneys familiar with patent law.

Indeed, the opposition procedure is specifically designed to allow the validity of a patent to be challenged, in particular in light of prior art documents unknown to the applicant and to the patent office when the application was filed!

Secondly, and even more controversially, this ruling can only encourage opponents to keep prior art documents to themselves, waiting for future appeal proceedings to produce them, in the certainty that the patentholder will not be able to defend themselves adequately. This is what motivates the radically different approach adopted by the EPO, which tends to consider new requests submitted at the appeal stage by the proprietor as admissible when they specifically address new factual grounds.

This ruling may also discourage patentholders from appealing against decisions of the Director General of INPI, even if they were adversely affected by the decision, and even if they have convincing arguments to assert their rights.

We can only hope that future case law from the Court will be more intent on preserving the rights of patent owners. Indeed, we believe it is essential that opposition proceedings allow third parties to challenge the validity of patents that were granted without all relevant information being known to the office during examination, while also safeguarding the protection legitimately due to the patentholder once this information has come to light.

Regimbeau's French Patent Attorneys remain at your disposal for opposition proceedings before INPI, as well as appeal proceedings before the French courts.