Joined Cases C-201/09 P and C-216/09 P: Judgment of the Court (Grand Chamber) of 29 March 2011 — ArcelorMittal Luxembourg SA, formerly Arcelor Luxembourg SA v European Commission, ArcelorMittal Belval & Differdange SA, formerly Arcelor Profil Luxembourg SA, ArcelorMittal International SA, formerly Arcelor International SA (C-201/09 P), European Commission v ArcelorMittal Luxembourg SA, formerly Arcelor Luxembourg SA, ArcelorMittal Belval & Differdange SA, formerly Arcelor Profil Luxembourg SA, ArcelorMittal International SA (C-216/09 P) (Appeals — Competition — Agreements, decisions and concerted practices — Community market in steel beams — Decision finding an infringement of Article 65 CS after the expiry of the ECSC Treaty on the basis of Regulation (EC) No 1/2003 — Powers of the Commission — Attributability of the unlawful conduct — Res judicata — Rights of the defence — Limitation period — Suspension of the limitation period — Effect erga omnes or inter partes — No statement of reasons)