What is antitrust law?

The core prohibitions

• Agreements between competitors to fix prices, rig bids, allocate customers or territories, or limit output. These are per se illegal — no defence of reasonableness is available, and they carry criminal penalties including prison for individuals.
• Monopolisation — not having market power, but acquiring or keeping it through exclusionary conduct rather than a better product.
• Mergers that may substantially lessen competition. Deals above the annual Hart-Scott-Rodino threshold must be notified and cleared before closing.
• Vertical restraints such as exclusive dealing and tying, judged under the rule of reason by weighing actual competitive effects.

No-poach and wage-fixing

Agreements between employers not to recruit each other's staff, or to fix wages, are treated as horizontal restraints among buyers of labour 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.

Private damages

Section 4 of the Clayton Act gives an injured party treble damages plus attorney fees, which is why private and class litigation dwarfs public enforcement in volume. Indirect purchasers cannot generally recover under federal law after Illinois Brick, but many states allow it under their own statutes.

Practical compliance

The rules that keep companies out of trouble are unglamorous: no discussion of pricing, capacity or customer allocation with competitors; counsel present at trade association meetings; written guidance on information exchange; and a leniency programme in mind, because the first conspirator to self-report can avoid criminal penalties entirely.