From the outset, the difficulty in applying the antitrust concept to organized labor has been that the two are intrinsically incompatible. The antitrust laws are designed to promote competition, and unions, avowedly and unabashedly, are designed to limit it. According to classical trade union theory, the objective is the elimination of wage competition among all employees doing the same job in the same industry. Logically extended, the policy against restraint of trade must condemn the very existence of labor organizations, since their minimum aim has always been the suppression of any inclination on the part of working people to offer their services to employers at different prices. Indeed, the initial reaction of the common law was to brand the concerted activities of labor unions, even those we today would term primary strikes, as criminal conspiracies. If labor organizations were to be legitimated despite our usual policies favoring wide-open competition, it would have to be on the basis of other, quite different societal values. By the time the Sherman Antitrust Act was passed in 1890, the courts had come to recognize the existence of those other, collective values, and had generally accepted the legality of peaceful strikes by employees against their employer for such purposes as higher wages and shorter hours.
St. Antoine, Theodore J. "Connell: Antitrust Law at the Expense of Labor Law." Va. L. Rev. 62 (1976): 603-31.