Case C-496/08 P: Judgment of the Court (Second Chamber) of 4 March 2010 — Pilar Angé Serrano, Jean-Marie Bras, Adolfo Orcajo Teresa, Dominiek Decoutere, Armin Hau, Francisco Javier Solana Ramos v European Parliament, Council of the European Union (Appeals — Officials — Success in internal competitions for change of category under the old Staff Regulations — Entry into force of the new Staff Regulations — Transitional rules for classification in grade — Plea of illegality — Acquired rights — Legitimate expectations — Equal treatment — Principle of sound administration and the duty to have regard for the welfare of officials)