Case T-669/14: Judgment of the General Court of 12 May 2016 — Trioplast Industrier v Commission (Competition — Agreements, decisions and concerted practices — Market in industrial plastic bags — Action for annulment — Challengeable act — Admissibility — Action for damages — Default interest — Concept of a debt which is certain, of a fixed amount and due — Proportionality — Legal certainty — Principle that penalties must be specific to the individual and to the offence — Lack of legal basis — Article 266 TFEU — Causal link)