Monopolization Under Sherman Act Section 2: Elements and Remedies

Monopolization under Section 2 of the Sherman Act is a federal felony, but being big is not the offense. To prove a violation, a plaintiff or prosecutor must show two things: the defendant holds monopoly power in a properly defined market, and it acquired or maintained that power through anticompetitive conduct rather than a better product, sharper strategy, or historical accident.¹ The statute reaches three distinct offenses — monopolization, attempted monopolization, and conspiracy to monopolize — and violations expose corporations to fines up to $100 million, individuals to fines up to $1 million and ten years in prison, and defendants in civil cases to treble damages plus attorney fees.

The Two-Part Test at the Core of Section 2

Courts do not punish dominance. They punish dominance that was won or kept by tactics that go beyond competition on the merits. A firm that captures 90 percent of a market by building something customers prefer has done nothing wrong. A firm that captures the same share by locking distributors into exclusive contracts designed to starve rivals of scale has a Section 2 problem.²

The analysis moves in a fixed order. First the court defines the market. Then it asks whether the defendant has monopoly power in that market. Then it asks whether the defendant did something exclusionary to acquire or keep that power. Each step has to hold up on its own, and each one is where cases actually get decided.

Step One: Defining the Market

Market definition sounds technical, and it is, but it decides the outcome of many cases before the merits are ever reached. Drawn too broadly, the defendant’s share shrinks and the claim collapses. Drawn too narrowly, a court may reject the definition entirely.

The Product Dimension

The product market includes every good or service that consumers treat as a reasonable substitute for the defendant’s offering. The economic question is cross-elasticity of demand: if the defendant raised prices, would enough customers switch away to make the increase unprofitable? Analysts often use the hypothetical monopolist test, which asks whether a single supplier of the proposed market could profitably impose a small but significant price increase — typically 5 to 10 percent — over a sustained period. If customers would defect to alternatives, those alternatives belong in the market.³

Submarkets can also exist within broader categories. In Brown Shoe Co. v. United States, the Supreme Court recognized that industry recognition, distinct product characteristics, specialized production, unique customers, distinct pricing, and specialized vendors can mark out a submarket as its own economic unit.⁴ A company that looks unremarkable in a wide market may dominate a well-defined slice of it.

The Geographic Dimension

The geographic market is the area where buyers can realistically turn for alternatives. For bulky goods, shipping costs may confine the market to a single metropolitan area. For software and digital services, the market may be national or global. Courts look at where customers actually buy, what it costs to ship, and whether distant sellers could feasibly enter in response to a price increase.

Step Two: Proving Monopoly Power

Once the market is defined, the question is whether the defendant controls it. Market share is the entry point. In United States v. Grinnell Corp., the Supreme Court found monopoly power where the defendant held 87 percent of the accredited central station security services market.⁵ As a working rule, shares above 70 percent create a strong inference of monopoly power. Shares between 50 and 70 percent can support a finding depending on other factors. Below 50 percent, monopolization claims rarely succeed.

Share alone is not decisive. A firm with 80 percent of a market that any competent rival could enter tomorrow has less real power than a firm with 60 percent in a market that nobody new can crack. Courts look at barriers to entry and expansion: capital requirements, proprietary technology, patents, long-term exclusive contracts that tie up distribution, and regulatory hurdles. The underlying question is whether the firm can sustain higher prices or degraded quality without triggering meaningful new competition.

Monopoly Power on Digital Platforms

Digital platforms complicate the analysis. Network effects can produce self-reinforcing dominance: each new user makes the platform more valuable to every other user, which draws still more users, which makes it harder for a superior newcomer to gain a foothold. The 2023 Merger Guidelines note that network effects “can create a tendency toward concentration in platform industries” and that smaller rivals face particular challenges in overcoming them.⁶

Switching costs and data lock-in reinforce the pattern. In United States v. Microsoft, the government proved an “applications barrier to entry” that locked users into Windows: switching operating systems meant losing access to thousands of applications written to Windows APIs.⁷ In United States v. Google (2024), a federal court found monopoly power in general search services based on a market share above 89 percent, combined with high capital costs, control of key distribution, brand strength, and scale advantages, and concluded that Google preserved this dominance through default agreements with browsers and device makers that foreclosed roughly 50 percent of all search queries.⁸

Step Three: Anticompetitive Conduct

Section 2 targets only the willful acquisition or maintenance of monopoly power through exclusionary conduct.² Aggressive competition is not the offense. The line between hard competition and illegal exclusion is where most Section 2 litigation lives.

Predatory Pricing

Predatory pricing is selling below cost to drive rivals out, then raising prices once they are gone. Under Brooke Group Ltd. v. Brown & Williamson Tobacco Corp., a plaintiff must prove two things: the defendant priced below an appropriate measure of its costs, and there was a dangerous probability the defendant could recoup the losses afterward.⁹ Recoupment is what makes these cases hard. In a market with easy entry, any post-predation price increase attracts fresh competition, so the strategy makes no economic sense.

Courts commonly use average variable cost as the cost benchmark.¹⁰ Prices above it are generally competitive. Prices below it suggest the firm is sacrificing profits to kill rivals. In Microsoft, the court found the company gave Internet Explorer away for free and paid other companies to distribute it, absorbing substantial costs specifically to destroy Netscape’s browser share.⁷

Tying

Tying conditions the purchase of one product on the buyer also taking a second, separate product. The concern is that a firm dominant in one market uses that leverage to force its way into another where it could not otherwise compete. In Microsoft, the government showed that bundling Internet Explorer with Windows and barring computer manufacturers from removing it used the operating system monopoly to dominate the browser market.⁷

Exclusive Dealing

Exclusive dealing arrangements require buyers or distributors to purchase only from one supplier. They are not automatically illegal. Courts apply the rule of reason, weighing the share of the market foreclosed against legitimate business benefits.¹¹ The Google decision shows how these arrangements can cross the line. Even where individual contracts were technically non-exclusive on paper, the court found that the collective effect of Google’s default agreements foreclosed rivals from the scale they needed.⁸

Refusal to Deal

Companies generally have no duty to do business with competitors. When a monopolist ends a profitable, long-running relationship with a rival for no reason other than to damage that rival, Section 2 can apply, but the Supreme Court has been skeptical. In Verizon Communications v. Trinko, the Court declined to impose a duty to deal and warned that forced sharing can reduce incentives for both the monopolist and its rivals to invest and innovate.¹² Refusal-to-deal claims face a steep climb.

The Business Justification Defense

A monopolist can defend its conduct by showing a legitimate business reason: improved product quality, lower costs, protection of intellectual property, or a genuine response to a competitive threat. Courts weigh procompetitive benefits against anticompetitive harms. If the same benefits could have been achieved through a less restrictive approach, the defense weakens. The justification must be real, and the conduct must actually serve it.²

Attempted Monopolization and Conspiracy

A firm does not have to succeed to violate Section 2. Attempted monopolization has three elements: anticompetitive or predatory conduct, specific intent to monopolize, and a dangerous probability of actually achieving monopoly power. In Spectrum Sports, Inc. v. McQuillan, the Supreme Court held that intent is never enough on its own. The plaintiff must also prove a realistic shot at capturing the market, which requires the same market analysis used for monopolization itself.¹³

Market share thresholds are lower for attempt claims. A share below 50 percent can support a claim if the firm’s position is rising quickly and it is using exclusionary tactics.¹⁴ Specific intent is usually inferred from the conduct itself. Colorful internal memos help, but courts weight the pattern of behavior more heavily than any single statement.

Conspiracy to monopolize is the third branch. It targets agreements between two or more independent parties to achieve monopoly control. The focus shifts to whether the agreement exists and whether the participants specifically intended to monopolize. Unlike attempted monopolization, conspiracy does not require a dangerous probability of success — the agreement, an overt act, and specific intent are enough.¹ Courts routinely infer agreement from circumstantial evidence, including actions against a firm’s individual self-interest that make sense only as coordination.

Penalties, Damages, and Deadlines

Section 2 violations are felonies. Corporate defendants face fines up to $100 million. Individuals face fines up to $1 million and prison sentences up to ten years.¹ Those caps can be exceeded under federal sentencing law, which permits fines up to twice the gross gain to the defendant or twice the gross loss to victims, whichever is greater.¹⁵ In practice, criminal prosecution for pure Section 2 monopolization is rare; the Justice Department reserves criminal antitrust for price-fixing and bid-rigging under Section 1.¹⁶

Civil enforcement is where most Section 2 action lives, and the exposure often dwarfs the criminal fines. Any person or business injured by a violation can sue in federal court and recover three times their actual damages plus the cost of the lawsuit, including reasonable attorney fees.¹⁷ The treble damages provision is designed to be punitive and to make private enforcement financially worthwhile. The federal government can also sue for treble damages when it is injured in its business or property.¹⁸

Private parties can also seek injunctions to stop ongoing conduct, though the plaintiff must show immediate danger of irreparable loss and post a bond.¹⁹ Government cases can pursue broader structural remedies, including divestiture and compulsory licensing. Enforcers generally prefer divestiture because a one-time structural fix is easier to administer than a behavioral order requiring years of monitoring.

Private antitrust suits must be filed within four years of when the cause of action accrued — when the plaintiff was injured or reasonably should have discovered the injury.²⁰ Four years can pass before a competitor squeezed by exclusive dealing understands what happened, and courts have developed doctrines that toll the clock when a defendant fraudulently concealed the conduct.

Who Can Bring a Section 2 Case

Enforcement authority is spread across several actors, and their tools differ.

The Department of Justice is the only federal agency that can bring criminal prosecutions under the Sherman Act, and it also brings civil cases seeking injunctions and structural remedies.
The Federal Trade Commission does not enforce the Sherman Act directly. Because Sherman Act violations also violate Section 5 of the FTC Act, the FTC brings equivalent cases under its own statute.¹⁶
State attorneys general can sue as parens patriae on behalf of their residents for treble damages.²¹
Private parties — any person or business injured by monopolistic conduct — can file in federal court, and this is the most common path for Section 2 enforcement in practice.

1
Office of the Law Revision Counsel. 15 USC 2 – Monopolizing Trade a Felony; Penalty
2
Federal Trade Commission. Monopolization Defined
3
U.S. Department of Justice. Operationalizing the Hypothetical Monopolist Test
4
Justia U.S. Supreme Court Center. Brown Shoe Co., Inc. v. United States, 370 US 294 (1962)
5
Justia U.S. Supreme Court Center. United States v. Grinnell Corp., 384 US 563 (1966)
6
U.S. Department of Justice. 2023 Merger Guidelines – Guideline 9
7
U.S. Department of Justice. United States v. Microsoft – Court’s Findings of Fact
8
Congressional Research Service. District Court Holds That Google Unlawfully Monopolizes Online Search
9
Justia U.S. Supreme Court Center. Brooke Group Ltd. v. Brown and Williamson Tobacco Corp., 509 US 209 (1993)
10
Federal Trade Commission. The Need for Objective and Predictable Standards in the Law of Predation
11
Legal Information Institute. Exclusive Dealing Arrangement
12
Justia U.S. Supreme Court Center. Verizon Communications Inc. v. Law Offices of Curtis V. Trinko LLP, 540 US 398 (2004)
13
Legal Information Institute. Spectrum Sports v. McQuillan, 506 US 447 (1993)
14
U.S. Department of Justice. Competition and Monopoly: Single-Firm Conduct Under Section 2 of the Sherman Act – Chapter 2
15
Office of the Law Revision Counsel. 18 USC 3571 – Sentence of Fine
16
Federal Trade Commission. Guide to Antitrust Laws
17
Office of the Law Revision Counsel. 15 USC 15 – Suits by Persons Injured
18
Office of the Law Revision Counsel. 15 USC 15a – Suits by United States
19
Office of the Law Revision Counsel. 15 USC 26 – Injunctive Relief for Private Parties
20
Office of the Law Revision Counsel. 15 USC 15b – Limitation of Actions
21
Office of the Law Revision Counsel. 15 USC 15c – Actions by State Attorneys General