On 22 October 2015, the Court of Justice rendered a judgment on appeal against the Commission decision in the Heat Stabilisers cartels (Commission v AC-Treuhand AG C-194/14 P). In this landmark judgment, the Court of Justice confirmed that a fine can be imposed under Article 101 TFEU on a consulting firm that provided services to the cartelists but is not present on the market where the infringements were committed.

On 11 November 2009, the Commission held AC-Treuhand liable for a total fine of EUR 348,000 for its participation in the Heat Stabilisers cartels. AC-Treuhand challenged the Commission decision before the General Court ("GC"), claiming that it provided certain services to the cartel but did not participate in an agreement or concerted practice. The GC, however, upheld the Commission decision and ruled that a consulting firm can be liable for an infringement of Article 101 when it actively and intentionally contributes to a cartel. This is the case even if the firm is present on a market other than the cartelised market.

AC-Treuhand appealed before the Court of Justice, arguing that its contracts with the cartelists had the object to provide services and that it did not participate in an agreement or concerted practice. Contrary to the Opinion of Advocate-General Wahl, the Court of Justice confirmed the judgment of the GC. According to the Advocate-General, AC Treuhand was not liable under Article 101 since it never exercised a competitive restraint on the participants of the cartel and thus was not able to restrict competition on the market in question.

The Court of Justice emphasized that Article 101 covers all agreements and concerted practices that distort competition, "irrespective of the market on which the parties operate and that only the commercial conduct of one of the parties need be affected by the terms of the agreements in question". Further, the Court of Justice found that AC-Treuhand's conduct was directly linked to the efforts of the cartelists. The purpose of the services was to attain, in full knowledge of the facts, the anti-competitive objects of the infringements. As a result, the Court of Justice concluded that AC-Treuhand did not provide mere peripheral services that were unconnected to the obligations assumed by the producers and the restrictions of competition. In its reasoning, the Court of Justice also considered that AC-Treuhand's interpretation of Article 101 "would be liable to negate the full effectiveness of the prohibition".

Further, the Court considered that, although Article 101 was never applied to cartel facilitators at the time of the infringements, AC-Treuhand could and should have expected that its conduct would infringe EU competition rules. The legality principle was thus not infringed.

AC-Treuhand also contested the imposition of a lump sum fine by the Commission. It argued that this constitutes a derogation from the 2006 Fining Guidelines and the Commission could have based the fine on the fees charged for the services provided to the participants of the infringements. The Court of Justice, however, also agreed with the GC's reasoning and rejected these arguments. The Court of Justice held that deviating from the Guidelines was permitted in this instance because AC-Treuhand was not present and had no sales on the cartelised market.  Further, it deemed that the fees charged by AC-Treuhand do not accurately reflect either the economic importance of the infringement or the extent of AC-Treuhand's participation.