The Future Adaptation of the Per Se Rule of Illegality in U.S. Antitrust Law

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William E. Kovacic


Judicial interpretation of § 1 of the Sherman Act has categorically forbidden certain forms of behavior. The characterization of conduct as “illegal per se” has powerful consequences in the government’s prosecution of civil and criminal cases under the Sherman Act and in the litigation of private claims for treble damages. The legitimacy and rationality of the U.S. antitrust system depend heavily upon the care and skill with which courts determine whether conduct is appropriate for summary condemnation or warrants a fuller assessment of its actual or likely effects. These determinations take place in a dynamic environment that features continuing adjustments in learning, in economics and law, about the competitive significance of specific practices. In light of antitrust law’s changing intellectual context, courts over time have made important additions to and subtractions from the category of conduct deemed to be illegal per se. This Article considers the process by which courts previously have performed this process of adaptation—to discern whether challenged behavior deserves abbreviated or more elaborate analysis. The Article suggests measures that could improve the quality of judicial efforts to adapt the application of the rule of per se illegality in the future. Among other steps, the Article describes how public antitrust agencies can use various policy tools (including guidelines, rules, research, public consultations, amicus briefs, and the selection of cases) to inform judicial judgments about whether to characterize behavior as illegal per se.

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The NYSBA 2020 William Howard Taft Lecture
How to Cite
William E. Kovacic. (2021). The Future Adaptation of the Per Se Rule of Illegality in U.S. Antitrust Law. Columbia Business Law Review, 2021(1). Retrieved from