US Antitrust Law

Statutory Framework

US antitrust law rests on three core federal statutes. The Sherman Act of 1890 prohibits contracts, combinations, and conspiracies in restraint of trade (§1) and monopolization, attempted monopolization, and conspiracies to monopolize (§2). The Clayton Act of 1914 addresses specific practices—mergers and acquisitions (§7), price discrimination (Robinson-Patman Act), exclusive dealing, and tying arrangements—where the effect “may be substantially to lessen competition.” The Federal Trade Commission Act of 1915 §5 prohibits “unfair methods of competition” and empowers the FTC to enforce antitrust law alongside the DOJ Antitrust Division. The Hart-Scott-Rodino Antitrust Improvements Act of 1976 established a mandatory premerger notification regime requiring parties to certain transactions to file with both agencies and observe a waiting period before consummation.

The Sherman Act: Section 1

Section 1 reaches only concerted action—agreements, whether written or tacit. The Supreme Court in Standard Oil Co. of New Jersey v. United States (1911) announced the rule of reason, under which only unreasonable restraints are unlawful. Certain categories of agreements—price fixing, bid rigging, market allocation, and group boycotts—are treated as per se unlawful, meaning no procompetitive justification is considered. In Leegin Creative Leather Products, Inc. v. PSKS, Inc. (2007), the Court overruled the per se ban on resale price maintenance, holding that vertical price restraints must be evaluated under the rule of reason.

The Sherman Act: Section 2

Section 2 targets unilateral conduct that monopolizes or threatens to monopolize a market. The offense requires (a) possession of monopoly power in a relevant market and (b) willful acquisition or maintenance of that power through exclusionary conduct as distinct from growth or development as a consequence of a superior product, business acumen, or historic accident. In United States v. Microsoft Corp. (D.D.C. 2001), the D.C. Circuit upheld findings that Microsoft unlawfully maintained its monopoly in Intel-compatible PC operating systems through anticompetitive licensing practices, bundling of Internet Explorer, and predatory tactics directed at Netscape and Java. The court applied the rule of reason framework to single-firm conduct and articulated a cautious approach to product design claims.

Clayton Act Merger Control

Section 7 of the Clayton Act prohibits acquisitions where the effect “may be substantially to lessen competition” or “to tend to create a monopoly.” The Horizontal Merger Guidelines (issued jointly by DOJ and FTC and updated in 2010 and 2023) articulate the analytical framework: market definition, concentration measurement (HHI), competitive effects analysis (coordinated and unilateral effects), entry analysis, efficiencies, and failing-firm defense. Vertical mergers are evaluated under the 2020 Vertical Merger Guidelines (withdrawn in 2021 but still informative).

FTC Act Section 5

Section 5 reaches conduct that violates the “spirit” of the antitrust laws or that constitutes an incipient violation. The FTC’s 2022 Policy Statement Regarding the Scope of Section 5 asserted that the Commission may challenge conduct beyond the reach of the Sherman and Clayton Acts, including conduct that tends to produce anticompetitive effects through non-price mechanisms such as data aggregation and algorithmic coordination.

Enforcement and Remedies

Private plaintiffs may seek treble damages (three times actual damages), injunctive relief, and attorneys’ fees under §4 of the Clayton Act. Indirect purchasers may recover under Illinois Brick Co. v. Illinois (1977) only where they purchase directly from the defendant, though many states have enacted Illinois Brick repealers permitting indirect-purchaser recovery under state law. The government may seek injunctive relief, structural remedies (divestiture), and criminal sanctions (fines and imprisonment) for Sherman Act violations.

Contemporary Developments

A bipartisan consensus has emerged around more vigorous antitrust enforcement. The 2021 Executive Order on Promoting Competition identified 72 initiatives across federal agencies. The FTC and DOJ have revised the merger guidelines to reflect a more interventionist approach, and litigation against Google (search monopolization), Meta (acquisitions), Amazon (monopolistic practices), and Apple (app-store exclusivity) signals a new enforcement era.