Presidential Decree on Maritime Agents (Article 8) applies to nationals and Agents of the EU/EEA that  may be licenced to provide their services; they also have to be certified for their command in Greek. The law allows for ship-owners self-providing these services.  See also: http://www.taxheaven.gr/laws/law/index/law/303 ; For Presidential Decree on Maritime Agents, see also: https://www.ynanp.gr/el/gia-ton-polith/nomo8esia/nomothesia-dieuthynse-limenikes-astynomilimenikes-astynomias/dla-genika/naytikoi-praktores-pd-2291995/ 