Joined Cases C-281/23 P and C-282/23 P: Judgment of the Court (Second Chamber) of 23 October 2025 – Polskie sieci elektroenergetyczne S.A., RTE Réseau de transport d’électricité, Svenska kraftnät, TenneT TSO BV v European Union Agency for the Cooperation of Energy Regulators (ACER) (Appeal – Internal market for electricity – Regulation (EU) 2019/942 – Board of Appeal of the European Union Agency for the Cooperation of Energy Regulators (ACER) – Regulation (EU) 2017/2195 – Articles 20, 21 and 37 – Balancing electricity – Transmission system operators – Establishment of European platforms for the exchange of balancing energy – European platform for the exchange of balancing energy from frequency restoration reserves with manual activation (mFRR platform) – European platform for the exchange of balancing energy from frequency restoration reserves with automatic activation (aFRR platform) – Development and approval of the implementation frameworks for those platforms – Functions required to operate those platforms – Cross-zonal capacity for the exchange of balancing energy – ACER decision rejecting the common proposal of the system operators)