The Clayton Act addresses specific practices that the Sherman Act does not clearly prohibit, such as mergers and interlocking directorates (that is, the same person making business decisions for competing companies). Section 7 of the Clayton Act prohibits mergers and acquisitions where the effect “may be substantially to lessen competition, or to tend to create a monopoly.” As amended by the Robinson-Patman Act of 1936, the Clayton Act also bans certain discriminatory prices, services, and allowances in dealings between merchants. The Clayton Act was amended again in 1976 by the Hart-Scott-Rodino Antitrust Improvements Act to require companies planning large mergers or acquisitions to notify the government of their plans in advance. The Clayton Act also authorizes private parties to sue for triple damages when they have been harmed by conduct that violates either the Sherman or Clayton Act and to obtain a court order prohibiting the anticompetitive practice in the future.
In addition to these federal statutes, most states have antitrust laws that are enforced by state attorneys general or private plaintiffs. Many of these statutes are based on the federal antitrust laws.