Opinion of Advocate General Biondi delivered on 5 June 2025.#Staten genom Sjöfartsverket v Stockholms Hamn AB.#Request for a preliminary ruling from the Stockholms tingsrätt.#Reference for a preliminary ruling – State aid – Agreement concluded before the accession of the Kingdom of Sweden to the European Union – Compensation for the loss of revenue arising from the abolition of passage fees for a lock – Concept of aid – Concept of undertaking – Economic activity – Existing or new aid.#Case C-401/24.