Cases T-516/18 and T-525/18: Judgment of the General Court of 12 May 2021 — Luxembourg and Others v Commission (State aid — Aid implemented by Luxembourg in favour of ENGIE — Decision declaring the aid incompatible with the internal market and unlawful and ordering its recovery — Tax rulings — State resources — Advantage — Combined effect of two tax measures — Participation exemption regime — Taxation of profit distributions — Abuse of law — Selectivity — Reference framework — Finding of a derogation — Comparability of situations — Parent-subsidiary arrangement — Group of companies — Recovery — Indirect harmonisation — Procedural rights — Obligation to state reasons)