... is here
https://ec.europa.eu/transport/sites...gencies_en.pdf
As mentioned in Section 7.1 of the Commission Interpretative Guidelines on Regulation (EC) No 261/20043, a passenger has the right to decide whether he/she wants to be represented by another person or entity, or not. However, a number of allegations of incorrect practices and misbehaviour by some claim agencies have been brought to the attention of the Commission.
Caveat Emptor