By institutionalizing its policy to grant lenient treatment1 and its method of setting fines,2 the European Commission has considerably curtailed its discretionary powers – delegated by Regulation 1/20033 – to sanction infringements of Article 81 EC. Moreover, it has given undertakings the possibility to calculate the costs of collusion and the benefits of applying for leniency when the Commission enforces against a cartel. If the costs of possibly being fined are sufficiently high and transparent, and the benefits of leniency are considerable and certain, early whistleblowing will be stimulated.4 The Commission’s leniency policy has already proven to be an effective tool for the destabilization of cartels.5 However, in the Community’s current decentralized enforcement system, cartels will be increasingly pursued by National Competition Authorities (‘NCAs’) pursuant to national procedures, which may differ greatly. As different sanctioning procedures imply different leniency policies, several national leniency schemes are operative parallel to the Commission’s Leniency Notice.6 It is questionable whether these diverging sanctioning procedures can effectively contribute to the destabilization of cartels. When the Commission does not enforce against a cartel, for example, due to lack of competence or prioritization,7 colluding undertakings could be prosecuted and sanctioned by NCAs under their respective national sanctioning schemes.8 Collaborating undertakings will then be ‘forced’ to file multiple leniency applications. Multiple leniency schemes consist of different, possibly conflicting criteria that will inevitably hamper transparency and certainty and therefore might endanger applications for leniency altogether. Furthermore, the fact that some Member...