What Was the Sherman Antitrust Act? Enforcement and Penalties

The Sherman Antitrust Act is the 1890 federal law that prohibits agreements restraining trade and prohibits monopolization of any part of interstate or foreign commerce. It is the foundation of American antitrust enforcement, with two operative sections: one aimed at collusion between separate businesses, and another aimed at a single company that dominates a market through anticompetitive conduct. Violations can be prosecuted criminally, challenged civilly by the government, or sued over privately by anyone injured.¹

What the Law Prohibits

The Act does two distinct things through two separate sections.

Section 1: Agreements That Restrain Trade

Section 1, codified at 15 U.S.C. § 1, bans agreements between two or more parties that restrain trade or commerce among the states or with foreign nations.¹ A written contract isn’t required. A verbal understanding or an informal handshake can be enough. What is required is more than one party; a single business acting alone cannot violate Section 1.

The most common Section 1 offenses:

Price-fixing, where competitors agree to set, raise, or stabilize prices instead of pricing independently.
Bid-rigging, where companies coordinate their bids so a pre-selected firm wins at an inflated price.
Market allocation, where competitors divide territories, customers, or product lines to avoid competing with one another.

The conduct must affect interstate or foreign commerce. Purely local dealings with no cross-border connection fall outside the statute. For foreign commerce, Section 1 reaches conduct that has a direct, substantial, and reasonably foreseeable effect on domestic commerce or imports.

Section 2: Monopolization

Section 2, codified at 15 U.S.C. § 2, targets a single company’s drive for market dominance. It prohibits monopolizing, attempting to monopolize, or conspiring to monopolize any part of interstate or foreign commerce.²

Being a monopoly, by itself, is not illegal. The Supreme Court’s decision in United States v. Grinnell Corp. requires two things for a Section 2 violation: monopoly power in the relevant market, and willful acquisition or maintenance of that power through anticompetitive conduct rather than through a superior product, business acumen, or historic accident.³

Monopoly power means the ability to control prices or exclude competitors without losing customers. Market share is a starting point. Courts have generally treated roughly 70 to 80 percent of a properly defined market as indicative of monopoly power, while a share below 50 percent rarely supports a monopolization claim. These are guidelines, not fixed rules; barriers to entry, the strength of remaining rivals, and overall market structure matter too.

The kinds of conduct that turn market dominance into a Section 2 violation include predatory pricing (selling below cost to drive out rivals, then raising prices), tying (forcing buyers to take an unwanted product to get the one they need), refusals to deal designed to starve competitors of essential inputs, and exclusive dealing arrangements that lock distributors out of carrying rival products.

Per Se Violations and the Rule of Reason

Not every agreement that touches competition breaks the law. Courts sort challenged conduct into two categories.

Some conduct is treated as automatically illegal — per se violations. Price-fixing, bid-rigging, and horizontal agreements among competitors to divide customers or territories fall here. The government does not need to prove market harm or weigh justifications; the agreement itself is the offense, because the conduct is so reliably harmful that excuses are not entertained.

Everything else is analyzed under the rule of reason, the standard the Supreme Court articulated in Standard Oil Co. of New Jersey v. United States in 1911.⁴ Under this approach, courts weigh anticompetitive harms against pro-competitive benefits like lower prices, better quality, or innovation, and decide whether the restraint is unreasonable on balance. Vertical agreements between a manufacturer and its retailers, exclusive dealing, and tying arrangements typically get rule-of-reason review. Some horizontal agreements do too, if they are ancillary to a legitimate joint venture or produce a genuinely new product.

What the Sherman Act Does Not Cover

Several categories of activity sit partly or fully outside the Act.

Nonprofit labor unions, agricultural cooperatives, and horticultural organizations are exempt, provided they are organized for mutual benefit rather than profit. Their members cannot be treated as an illegal conspiracy for pursuing the organization’s lawful aims.⁵

The business of insurance is primarily regulated by state law under the McCarran-Ferguson Act. Federal antitrust laws apply to insurance only to the extent state law does not already regulate the activity. The exemption does not cover boycotts, coercion, or intimidation.⁶

Under the state-action doctrine from Parker v. Brown (1943), state and local governments are immune from federal antitrust liability for actions taken under a clearly expressed state policy that foreseeably displaces competition. Private parties can claim the same immunity when they act under a clearly articulated state policy and are actively supervised by the state.

Who Enforces the Sherman Act

Two federal agencies share enforcement responsibility. The Department of Justice Antitrust Division is the only agency that can bring criminal prosecutions. Its criminal work focuses on hard-core cartel conduct like price-fixing and bid-rigging, and it can seek prison time, fines, and extradition of foreign defendants.⁷

The Federal Trade Commission investigates potential violations and brings civil enforcement actions, including injunctions against anticompetitive conduct and civil penalties for violations of FTC orders. Both agencies can issue civil investigative demands to compel documents and testimony.⁸

Private Lawsuits and Treble Damages

The Act is not enforced only by the government. Any person or business injured by a violation can sue in federal court, and a successful plaintiff recovers three times the actual damages proven, plus the cost of the lawsuit and reasonable attorney fees.⁹ The court may also award prejudgment interest on actual damages from the filing date through judgment. A defendant that caused $10 million in provable harm can face a $30 million judgment plus the plaintiff’s legal costs.

One important limit: under Illinois Brick Co. v. Illinois, only direct purchasers can sue for damages under federal antitrust law.¹⁰ If a manufacturer overcharges a distributor and that overcharge is passed along to a retailer or consumer, the downstream buyer generally cannot sue the manufacturer in federal court. Many states allow indirect-purchaser suits under their own antitrust laws.

The DOJ Leniency Program

The Justice Department runs a Corporate Leniency Program that offers full immunity from criminal prosecution to the first company in a cartel that reports its conduct and cooperates.¹¹ If no investigation is already underway, immunity is automatic. Even after an investigation has begun, amnesty may still be available to the first qualifying applicant. Cooperating officers, directors, and employees are protected along with the company. Only one company per conspiracy can receive leniency, which creates a strong incentive to report before a competitor does.

Criminal Penalties

Criminal violations of Section 1 or Section 2 are felonies with identical maximum penalties. Corporations face fines of up to $100 million per offense.¹ Individuals face fines of up to $1 million, up to 10 years in prison, or both.²

The statutory cap is not always the ceiling. Under a separate federal sentencing statute, if the defendant’s financial gain from the crime or the victims’ financial loss exceeds the statutory maximum fine, the court can impose a fine of up to twice the gross gain or twice the gross loss, whichever is greater.¹² In large cartel cases, this calculation regularly pushes actual fines well above $100 million.

Why Congress Passed It

The Sherman Act was a response to the industrial trusts of the late 19th century. Shareholders of competing companies handed their stock to a single board of trustees, effectively merging rivals while keeping them legally separate. Petroleum, railroads, sugar, and steel were dominated by these arrangements. Standard Oil, controlled by John D. Rockefeller, controlled roughly 90 percent of American oil refining by the 1880s and used that position to dictate prices nationwide.

Congress passed the Act on July 2, 1890. The law authorized the federal government to bring proceedings against trusts and dissolve them, the first time the federal government directly regulated industrial competition on a national scale. Its language was broad and its key terms undefined, which limited its bite until the courts developed workable standards over the following decades.¹³ The 1911 Standard Oil decision, which broke up the trust and introduced the rule of reason, was the turning point in giving the statute practical force.

1
Office of the Law Revision Counsel. 15 USC 1 – Trusts, Etc., in Restraint of Trade Illegal; Penalty
2
Office of the Law Revision Counsel. 15 USC 2 – Monopolizing Trade a Felony; Penalty
3
Justia U.S. Supreme Court Center. United States v. Grinnell Corp., 384 U.S. 563 (1966)
4
Justia U.S. Supreme Court Center. Standard Oil Co. of New Jersey v. United States, 221 U.S. 1 (1911)
5
Office of the Law Revision Counsel. 15 USC 17 – Antitrust Laws Not Applicable to Labor Organizations
6
Office of the Law Revision Counsel. 15 USC 1012 – Regulation by State Law; Federal Law Relating Specifically to Insurance
7
United States Department of Justice. Antitrust Division – Criminal Enforcement
8
Federal Trade Commission. A Brief Overview of the Federal Trade Commission’s Investigative, Law Enforcement, and Rulemaking Authority
9
Office of the Law Revision Counsel. 15 U.S. Code 15 – Suits by Persons Injured
10
Justia U.S. Supreme Court Center. Illinois Brick Co. v. Illinois, 431 U.S. 720 (1977)
11
U.S. Department of Justice. Status Report – Corporate Leniency Program
12
Office of the Law Revision Counsel. 18 U.S. Code 3571 – Sentence of Fine
13
National Archives. Sherman Anti-Trust Act (1890)