After grant of a European patent, it is possible to file an opposition against it, within a 9-month period from the publication of the mention of grant in the European Patent Bulletin.
This procedure may allow third parties to avoid national procedures of cancellation for invalidity or revocation of the patent. Indeed, if the European patent is refused after the opposition procedure, or if the scope of the claims is reduced, the decision takes effect in all the countries where the European patent was validated.
An opposition can be filed by anyone. It is even possible to file an opposition in the name of the European patent attorney (as a straw man) in order not to reveal the true identity of the opponent.
According to Article 100 of the EPC, an opposition may be filed on the grounds that:
The opposition notice is forwarded to the patentee, who is given a 4-month period to file observations in response to the opposition. This period of 4-month can be extended upon request.
In the case where more that one opposition is filed against the same patent, all oppositions are joined. It is for example possible to combine documents cited by different opponents.
The patentee at this stage may file a main request of claims (amended or not), and one or more auxiliary requests of amended claims.
Even in the absence of observations filed by the patentee, the EPO will examine the case.
After some time, which can be rather long, the Opposition Division can give an intermediate decision. If oral proceedings were requested by the opponent or the patentee, the Opposition Division will set a date for the hearing.
During the hearing, the Opposition Division interviews each party on specific points. All the requests of the patentee are studied in the order indicated by the patentee. Only Claim 1 of each request is studied, if Claim 1 of the Main Request lacks novelty for example, the Opposition Division then studies Claim 1 of the First Auxiliary Request. It is not possible during the hearing to introduce a new request.
A decision on each request is taken immediately by the Opposition Division.
When Claim 1 of a request is considered as patentable, new, inventive and not extending beyond the content of the application as filed, this request constitutes the set of claims of the patent maintained as amended after opposition.
If none of the requests are deemed patentable, new, inventive and not extending beyond the content of the application as filed by the Opposition Division, the patent is revoked.
No observation or requests can be filed after the hearing. The decision is therefore immediately known at the time of the hearing. A written decision is then sent to the patentee and to the opponent(s) by the Opposition Division.
Any party adversely affected by the decision of the Opposition Division may file a notice of appeal, due within an non-extendable period of 2 months from the date of the written decision. The statement of grounds for the appeal must be filed within 4 months from the date of the written decision.