	Introduction

Antitrust doctrine holds that robust competition will best protect consumers; it is concerned with the viability of individual competitors only insofar as their fates affect marketplace competitiveness. Although there are general prohibitions against monopolization and attempted monopolization in the Sherman and Clayton Acts, and a prohibition against "unfair acts" in commerce in section 5 of the Federal Trade Commission Act, "monopoly" and "monopolist" are merely descriptive terms, used to illustrate a situation in which a single entity possesses effective control of the market in which it operates. Neither term implies anything about the lawfulness of the monopoly possessed: there is no concept of "no fault" monopolization in United States antitrust law. Monopoly and Monopolization

Although monopoly and monopolization are fundamental, and related, concepts in antitrust law, they are not synonymous. The Concept and Importance of "Relevant Market"

Whether a market entity is considered a monopolist, or whether it can be successfully charged with either having attempted to monopolize a market or actively monopolizing a market depends on the definition of the market in which it operates. Duty of Monopolist to Deal

			In general

The basic antitrust truth, expressed in 1919 by the Supreme Court in United States v. Colgate & Co. , notwithstanding certain exceptions and attempts to circumscribe it, remains that an entity—even a monopolist—is free to deal or not deal with any other entity unless its actions constitute either "guilty behavior" or an attempt to expand its monopoly into a market adjacent to the one in which it may hold a lawful monopoly:
In the absence of any purpose to create or maintain a monopoly, the [Sherman] act does not restrict the long recognized right of trader or manufacturer engaged in an entirely private business, freely to exercise his own independent discretion as to parties with whom he will deal; and, of course, he may announce in advance the circumstances under which he will refuse to sell. "Essential facilities" doctrine

From almost the beginning of statutory antitrust law (the enactment of the Sherman Act in 1890), the concept of the so-called "essential facilities" doctrine has been developing; courts have rather consistently held that a monopolist who controls an instrumentality that is crucial to the ability of a potential competitor to compete and which cannot be reasonably duplicated by the potential competitor must make that facility available to him. Verizon v. Trinko

Curtis Trinko challenged, as a violation of the antitrust laws, Verizon's failure to adequately share its network facilities with his provider of telecommunications service, as required by the Telecommunications Act of 1996. The duty to deal with actual or potential competitors of a lawful monopolist who has not been found to have engaged in some "guilty behavior" is generally governed by the Colgate doctrine, which gives market participants the right to choose their commercial relationships. In Verizon Communications, Inc. v. Trinko , however, the Supreme Court questioned the validity of the "essential facilities" doctrine in antitrust law—at least in the context of regulated entities.
Antitrust law does not mandate either that markets be competitive, or that they contain some predetermined number of participants/competitors; it is concerned, rather, with the operation of markets, on the assumption that a properly functioning market (i.e., one in which there is an opportunity for viable competition, and is not skewed by the predatory actions of participants), will best protect consumers. "Monopoly" and "monopolist" are, therefore, merely descriptive terms, used to illustrate situations in which a single entity (or group of entities) possesses effective control of the market in which it operates; neither term implies anything about the lawfulness of the monopoly possessed. "Monopolization," on the other hand, is the term used in antitrust law to characterize as unlawful a situation in which a monopolist—irrespective of whether his monopoly has been lawfully achieved—couples his monopoly status with behavior designed to unfairly exploit, maintain, or enhance his market position. Similarly, "attempted monopolization"connotes a situation in which an entity unlawfully or unfairly attempts to secure a market monopoly. The long-standing, judicially created Rule of Reason, which involves balancing an anticompetitive action with any procompetitive results, underscores those facts.
Whether a market participant who is a monopolist must deal with anyone who desires to deal with it continues to be largely governed by the so-called Colgate doctrine. In 1919, in United States v. Colgate & Co. (250 U.S. 300), the Supreme Court recognized the unfettered "right" of a private vendor "to exercise his own independent discretion as to parties with whom he will deal ...." Colgate notwithstanding, the existence of an "essential facility" (i.e., a necessary component of a potential competitor's business and which is both unavailable from any source other than the alleged monopolist and cannot be reasonably duplicated), once established, has generally been thought to impose a duty to deal with the actual or potential competitors of even a lawful monopolist. The continuing viability of the so-called "essential facilities" doctrine, however, was called into question by the Supreme Court's 2004 ruling in Verizon v. Trinko (540 U.S. 398).
The Antitrust Division of the Department of Justice (DoJ) and the Federal Trade Commission (FTC) each operate on the assumption that the monopoly status of competitors is antitrust-relevant only insofar as their actions may impact the operation or competitiveness of markets.
This report—which explores the difference between monopoly and monopolization as those terms are used in antitrust law, and the differing enforcement consequences of each—will be updated if case law or legislation alters the concepts it discusses. It is based on several existing documents by the same author, including CRS Report RS20241, Monopoly and Monopolization - Fundamental But Separate Concepts in U.S. Antitrust Law; CRS Report RS21723, Verizon Communications, Inc. v. Trinko: Telecommunications Consumers Cannot Use Antitrust Laws to Remedy Access Violations of Telecommunications Act; and Duty of a Monopolist to Deal, a general distribution memorandum.