Anonymous Oppositions to continue at the European Patent Office

by Dr. Markus Grammel | 12. August 2021 | Know-How

Following the grant of a European patent there is a time window of nine months – the so-called opposition period – during which oppositions can be filed against a granted patent and revocation of the patent can be requested. Grounds for opposition are lack of novelty, lack of inventive step, lack of sufficiency of disclosure and whether the patent extends beyond the content of the application as originally filed. If one of these grounds applies, the European Patent Office (EPO) revokes the patent.

The current practice of the EPO allows an opposition to be validly filed by a “straw man” meaning by an opponent filing the opposition not in their own interest, but in the interest of an anonymous third party. Typically, in these cases, a law firm acts as the opponent and the representative at the same time, to protect the identity of the client. This practice has been challenged numerous times over the years, most recently in the case underlying decision T 1839/18, in which the Board confirmed the legality of the practice.


In the opposition appeal proceedings underlying decision T 1839/18, the patent proprietor challenged the admissibility of the opposition. The patent proprietor argued, among other things, that the opponent had no legitimate interest in filing the opposition. In support, the proprietor referred to decision G 1/06 of the Enlarged Board of Appeal, which the proprietor interpreted as stipulating a general requirement for a “legitimate interest” in any procedural act taken before the EPO. The Board in T 1839/18 did not follow the proprietor’s interpretation. Rather, the Board emphasized that essentially any filed opposition was in the interest of the public by:

a) revoking undeserved monopolies or reducing them to the actually deserved scope;

b) fostering industrial development by preventing that innovation is led astray by wrongfully granted monopolies; and by:

c) enhancing legal certainty.

In the end, the Board found that the term straw man is in fact misguided, since no interest in filing an opposition has to be proven.

In conclusion the Board confirmed the established practice of filing an opposition at the behest of a third party, whose identity is not revealed, without indicating this fact to the EPO.


There are many reasons for filing anonymous oppositions at the EPO. For instance, potential infringers may want to move against a patent without alerting the patent proprietor to their potential infringing activities. Sometimes the reason for filing an anonymous opposition is to protect commercial relationships with the patent proprietor. Anonymity also helps to avoid arguments that are made during opposition proceedings being held against the potential infringer in later infringement proceedings.


Keeping anonymity sometimes comes at a price. For instance, attending oral proceedings with the professional representative may not be possible without revealing the identity of the interested third party. More relevantly, one may be blocked from successfully making certain requests that are only justified by the interested third party.

For example, a request for expedited proceedings that applies if the reason for expediting the proceedings only relates to the anonymous third party. In case T 872/13 a request for expedited proceedings was denied, because the underlying grounds that could have justified accelerating the processing did not pertain to the straw man opponent, but to a company that was not party to the proceedings. Maintaining anonymity may also reduce the probative value of experimental evidence if it prevents revealing the identity of the person that has carried out the experiments (T 103/15).


In summary, oppositions can be filed anonymously with the EPO by making use of a straw man opponent. The so-called straw man oppositions can be very helpful to protect commercial interests. However, oppositions may also have negative consequences. Therefore, it is important in each individual case to weigh the benefits of staying anonymous against potential pitfalls.

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