Case C-5/16: Judgment of the Court (Second Chamber) of 21 June 2018 — Republic of Poland v European Parliament, Council of the European Union (Action for annulment — Decision (EU) 2015/1814 — Determination of legal basis — No taking into account of the effects of a measure — Article 192(1) TFEU — Article 192(2)(c) TFEU — Measures significantly affecting a Member State’s choice between different energy sources and the general structure of its energy supply — Principle of sincere cooperation — Article 15 TEU — Powers of the European Council — Principles of legal certainty and protection of legitimate expectations — Principle of proportionality — Impact assessment)