Judgment of the Court (Grand Chamber) of 27 January 2026.#European Commission v Hungary.#Failure of a Member State to fulfil obligations – Article 258 TFEU – Admissibility – Decision (EU) 2021/3 – Position to be taken, on behalf of the European Union, at the reconvened sixty-third session of the Commission on Narcotic Drugs, established by the United Nations Economic and Social Council, on the scheduling of cannabis and cannabis-related substances under the Single Convention on Narcotic Drugs of 1961, as amended by the 1972 Protocol, and the Convention on Psychotropic Substances of 1971 – Position and vote of a Member State, both being contrary to that position of the European Union – Article 4(3) TEU – Principle of sincere cooperation – Effects of the alleged conduct as at the date of expiry of the deadline laid down in the reasoned opinion – Ongoing effects on the unity and consistency of the European Union’s international action – Article 3(2) TFEU – Exclusive external competence – Effect on common rules or alteration of their scope – Plea of illegality raised in the defence