The Advocate General’s Opinion supports one of Lafarge SA’s claims in its appeal to the European Court of Justice (ECJ) to set aside earlier rulings by the Court of First Instance (CFI) (now the General Court) regarding its participation in a plasterboard cartel (in case C-413/08 P). The construction materials firm was one of four companies fined by the Commission in 2002 for its participation in the cartel. The CFI dismissed Lafarge’s appeal against the fine in 2008 (T-54/03). Thereafter, Lafarge took a case before the ECJ claiming that the CFI had made several errors in law. In his Opinion of 11 February 2010, Advocate General Mazak recommended that the ECJ reject the majority of Lafarge’s grounds for review. These included claims that the CFI had distorted the facts in its reading of the case, infringed several key legal principles including those concerning the burden of proof and proportionality, and made a number of errors in law in its assessment of the Commission’s decision and the penalties imposed. However, he did find merit in Lafarge’s contention that the CFI failed to properly address a plea of unequal treatment over whether Lafarge had participated in a single, complex and continuous infringement from 1992 and recommends that this issue should be referred back for reconsideration.