Judgment of the Court (First Chamber) of 19 September 2024.#Autorità per le Garanzie nelle Comunicazioni and Others v Telecom Italia SpA and Others.#Reference for a preliminary ruling – Electronic communications networks and services – Universal service and users’ rights – Directive 97/33/EC – Article 5 – Directive 2002/22/EC – Article 13 – Financing of universal service obligations – Concept of ‘unfair’ or ‘undue’ burden – Definition of the entities participating in the mechanism for financing the net cost of those obligations – National legislation providing for the participation of mobile telephone operators in that mechanism – Criteria – Degree of substitutability between fixed telephony services and mobile telephony services.#Case C-273/23.