Case C-181/23: Judgment of the Court (Grand Chamber) of 29 April 2025 – Commission v Malta (Citizenship by investment) (Failure of a Member State to fulfil obligations – Article 20 TFEU – Citizenship of the Union – Article 4(3) TEU – Principle of sincere cooperation – Principle of mutual trust between the Member States – Grant of the nationality of a Member State – Special relationship of solidarity and good faith – Operation of an investor citizenship scheme – Naturalisation in exchange for predetermined payments or investments – Transactional nature of the naturalisation scheme, which amounts to the commercialisation of Union citizenship)