What is antitrust law?

Why it exists

Competition keeps prices down, quality up and innovation moving. Antitrust law, which began with the Sherman Act of 1890 in response to the oil and railroad trusts, stops businesses from getting around competition by agreeing not to compete or by using power to shut rivals out. It does not punish a company simply for being big or successful.

The core prohibitions

• Agreements between competitors to fix prices, rig bids, allocate customers or territories, or limit output. These are per se illegal — no defense of reasonableness is available — and they carry criminal penalties, including up to 10 years in prison for individuals and fines of up to $100 million for companies, or more based on gain or loss.
• Monopolization — not having market power, but acquiring or keeping it through exclusionary conduct rather than a better product, better business sense or historical accident.
• Mergers that may substantially lessen competition. Deals above the annual Hart-Scott-Rodino threshold must be notified to the FTC and DOJ and cleared before closing.
• Vertical restraints such as exclusive dealing, tying and certain resale price agreements, judged under the rule of reason by weighing actual competitive effects.
• Price discrimination between business buyers that harms competition, under the Robinson-Patman Act.

An agreement does not have to be written

Price-fixing cases often rest on informal understandings — a nod at a trade show, a pattern of text messages, sharing future pricing plans through a third party. Algorithmic pricing tools that pool competitors' confidential data have become a recent focus of enforcers and private suits. Parallel conduct alone, such as competitors independently matching each other's prices, is not illegal without evidence of an agreement.

No-poach and wage-fixing

Agreements between employers not to recruit each other's staff, or to fix wages, are treated as restraints among buyers of labor and have been prosecuted criminally. This is the area where ordinary businesses most often stumble into serious exposure, usually through an informal understanding at an industry meeting or between franchisees.

Private damages

Section 4 of the Clayton Act gives an injured business or consumer three times its damages plus attorney fees, which is why private and class litigation far exceeds public enforcement in volume. Indirect purchasers cannot generally recover under federal law after Illinois Brick (1977), but many states allow it under their own statutes. The federal limitations period is four years.

How investigations begin

Through complaints from customers or competitors, merger filings, whistleblowers and, most often in cartel cases, leniency applications. The DOJ's leniency program lets the first conspirator to self-report and cooperate avoid criminal charges entirely, which creates a race to confess once a cartel starts to unravel.

Practical compliance

The rules that keep companies out of trouble are unglamorous: no discussion of pricing, capacity, bids or customer allocation with competitors; lawyers present or agendas reviewed at trade association meetings; written guidance on what information may be exchanged; care with employee non-solicitation clauses; and training for sales staff. If a competitor raises pricing at a meeting, object, leave and document that you left.

If you think you were harmed

Businesses shut out of a market or forced to pay inflated prices may have claims. An antitrust lawyer can evaluate the market and damages; many such cases are brought as class actions on contingency.

Examples of cases

Well-known enforcement includes the breakup of Standard Oil (1911) and AT&T (1984), the DOJ case against Microsoft over browser bundling around 2000, and more recent monopolization cases against major technology companies — in 2024 a federal court found that Google had unlawfully maintained a monopoly in general search. Cartel prosecutions regularly involve auto parts, generic drugs, poultry and construction bids. Merger challenges have blocked or reshaped deals in groceries, airlines, hospitals and publishing.

State antitrust laws

Every state has its own antitrust statute, often modeled on the Sherman Act, and state attorneys general bring cases under both state and federal law — frequently joining together in multistate actions. Some states, such as California, reach conduct the federal law does not.