On 12 November 2014, the Court of Justice published its judgment regarding Guardian's appeal against the General Court's ("GC") ruling in the flat glass cartel. With reference to the principle of equal treatment, the Court of Justice found that the GC had partially erred in law when it rejected Guardian's earlier appeal against the imposition of a EUR 148 million fine by the Commission. The Court of Justice therefore decided to reduce the fine by 30% to EUR 103.6 million.

On appeal before the Court of Justice, Guardian argued that the GC had failed to apply the principle of equal treatment correctly by upholding the Commission's original decision. In that decision, the Commission had, for the purpose of calculating the amount of the fines, limited itself to the participants' external sales (sales to independent third parties) thereby excluding internal sales (sales between entities belonging to the same undertaking). This meant that the relative weight of one of the other participants in the infringement (a vertically integrated company) was reduced whereas that of Guardian (a non-vertically integrated company) was increased commensurately.

Guardian accordingly argued that the GC had failed to ensure that the fines imposed by the Commission would not discriminate between vertically integrated and non-vertically integrated firms. The Court of Justice accepted this reasoning. It subsequently decided to substitute its own appraisal for the Commission's and reduced Guardian's fine by 30%.

This judgment represents a fairly rare instance in which the Court of Justice reduced the amount of a fine upheld earlier by the GC. It also provides further guidance as to how the amount of a fine should be calculated in the light of the principle of equal treatment. In that respect, the Court of Justice has made clear that the method for calculating fines should include both internal and external sales in order to avoid discriminatory outcomes between vertically integrated and non-vertically integrated firms.