This Article (1) articulates operational definitions of eight possible morally-defensible test of antitrust legality, (2) describes the conduct-coverage of, tests of prima facie illegality promulgated by, and economic-efficiency defenses recognized by U.S. and E.U. antitrust law correctly interpreted as matters of law, (3) delineates the seven most important differences between U.S. and E.U. antitrust law as written and the two most important shared attributes of U.S. and E.U. antitrust law as written, and (4) evaluates the relative and absolute moral desirability of these two antitrust-law regimes as written from the perspectives of both the liberal conception of justice and various nonliberal conceptions of the moral good. Inter alia, the Article explains why (1) conduct that manifest one or more perpetrators’ specific anticompetitive intent or distorts competition (constitutes unfair competition) violates liberal moral-rights, (2) conduct that manifests specific anticompetitive intent, lessens competition or distorts competition is distributively undesirable from utilitarian, various nonliberalegalitarian and various individual history/conduct-focused normative perspectives, and (3) analyses that take appropriate account of the General Theory of Second Best reveal that (A) although the fact that conduct reduced price competition in some area of product-space does not imply that it generated economic inefficiency by causing too few resources to be devoted to unit-output production in that area of product-space relative to the amount devoted to unit-output product elsewhere, it does imply that the relevant conduct generated economic inefficiency by allocating resources from unit-output production to quantity-or-variety-increasing-investment (QV-investment) creation, (B) price-fixing and predatory pricing generate economic inefficiency not only by generating allocative transaction costs but by leading to undercutting by competitive inferior’s and retaliation that results in suppliers’ that are allocatively as well as privately worse-than-best-placed making sales, (C) conduct that reduces QV-investment competition increases economic efficiency by allocating resources from QV-investment creation t unit-output production and production-process-research execution, and (D) the use of many pricing-techniques (price discrimination, the simultaneous charging of lump-sum fees and * The University of Texas at Austin, Austin, TX, USA Corresponding Author: Richard S. Markovits, The University of Texas at Austin, Austin, TX 78712, USA. Email: firstname.lastname@example.org The Antitrust Bulletin 2017, Vol. 62(3) 514-590 ª The Author(s) 2017 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0003603X17719763 journals.sagepub.com/home/abx per-unit prices, and some functional types of tie-ins and reciprocity) is economically inefficient although it does not manifest the perpetrator’s specific anticompetitive intent or lessen competition.