In the U.S., private antitrust enforcement plays a large role in the general enforcement scheme of the antitrust laws. Companies that plead guilty or are convicted of price-fixing generally pay fines but not restitution to victims—private litigation is assumed to be sufficient to compensate victims. The threat of treble damages in private actions (both individual and class actions) is significant, and often aggrieved parties can win more in damages than the government is able to recover and fine. And the chance to “detreble” damages by cooperating with plaintiffs can play a large role in a company's decision to participate in the Antitrust Division's leniency program.

The effects of such private suits are blunted in the European Union.

Under EU competition law, individual businesses and consumers that suffer harm have the right to file for damages in a national court. The European Court of Justice (ECJ) has even emphasized that these types of suits are an integral part of the EU's antitrust scheme. Without a right for private damages claims, the practical effects of the EU's laws prohibiting anticompetitive conduct “would be put at risk,” the court said in a 2001 opinion in Courage Ltd. v Bernard Crehan, a U.K. case. “Indeed,” the court continued, “the existence of such a right strengthens the working of the Community competition rules and discourages agreements or practices, which are frequently covert, which are liable to restrict or distort competition.”