In T 227/92 it was held that a sub-authorisation from a professional representative to a person who was not a professional representative within the meaning of Art. 134 EPC 1973 was invalid. The latter person's role was therefore limited to that of technical adviser to the professional representative.

In T 382/03 the previous representative, Mr E. of UDL, filed a fax to announce that Mr U., who was not a member of that association, would appear for respondent 1 at the oral proceedings before the board. Mr E. did not notify the board that his association's authorisation was terminating. Hence, that was a situation where the President's decision required the new representative, Mr U., to prove that he was authorised to act on behalf of respondent 1. As Mr U. did not refer to a general authorisation from respondent 1, proof of an individual authorisation had to be provided to the board. In principle, that could be done by filing a direct individual authorisation from opponent 1, or by filing a sub-authorisation from an authorised representative who was entitled to sub-authorise a third representative. In view of the sub-authorisation from UDL submitted by Mr U. at the oral proceedings, the only issue remaining was whether or not UDL was entitled to give such a sub-authorisation.

For an example of a professional representative entitled by a chain of sub-authorisations to make submissions on behalf a party, see T 1081/06.

In T 1676/08, the board had no reason in the circumstances of the specific case to doubt that Mr S, a legal practitioner entitled to act as a representative, was duly sub-authorised. Moreover, on the same day of the oral proceedings, the professional representative, Mr M, stated as a precautionary measure that he endorsed any submission made by Mr S during these oral proceedings.

In T 1693/10, the contested sub-authorisation given to a second professional representative had eventually been withdrawn. This second representative was regarded from then on as assisting the first representative as an "accompanying person" within the meaning of G 4/95 (OJ 1996, 412) but was not permitted to speak at the oral proceedings because at least one of the criteria laid down in that decision for such permission had not been met.

In T 2453/12 opponent 2's notice of opposition had been filed under the name of an already defunct company and rejected as inadmissible by the opposition division at the oral proceedings. Its representative had then been issued with authorisation to act for opponent 1 during the remaining proceedings. The patent proprietor (respondent) took the view that one opponent's representative could not now act for the other opponent too. The opponents argued that opponent 1's original representatives – who were anyway its employees – remained authorised to represent it and that the appeal lodged by those representatives was therefore admissible. Opponent 1 had merely issued opponent 2's representative with a sub-authorisation during the opposition proceedings. The board observed that, under Art. 133(1) and (3) EPC, legal persons having their principal place of business in an EPC contracting state were not compelled to be represented by a professional representative in EPO proceedings and were instead free to have a duly authorised employee act for them. That applied irrespective of whether they chose also to authorise a professional representative in parallel; parties could never deprive themselves of the right to represent themselves by issuing authorisations. For that reason alone, there could be no doubt that opponent 1's in-house representatives had been entitled to lodge its appeal.