In the case of American Federation of Musicians of the United States and Canada et al. v. Carroll et al., 1967, the Supreme Court ruled in favor of a group of musicians who were not members of the American Federation (AFM), but had been hired to perform at a Detroit hotel. The AFM sought to prevent them from performing because they weren't union members, arguing that their bylaws allowed them to do so under federal labor law exemptions for "legitimate labor objectives." However, these non-union musicians sued on antitrust grounds claiming that this was an illegal restraint on trade. The Supreme Court held that while unions are generally exempt from antitrust laws when pursuing legitimate labor goals such as collective bargaining or striking, this exemption does not extend to all activities merely because they might affect wages or working conditions. In this case, it found no evidence supporting AFM's claim that barring non-members from employment served any legitimate union objective related directly to wage rates or working conditions; therefore its actions constituted an unlawful boycott violating Sherman Act’s prohibition against restraints on trade.

In the dissenting opinion for the American Federation of Musicians v. Carroll case, it was argued that there is a significant difference between an employer and a labor organization in terms of their economic power and ability to impose restraints on trade. The majority's decision failed to recognize this distinction, which led them to apply antitrust laws designed for business enterprises onto labor organizations - something that Congress did not intend when they enacted these laws. Furthermore, the dissent pointed out that applying such laws could potentially undermine collective bargaining rights protected by federal law. They also disagreed with the majority's interpretation of certain provisions within union agreements as being inherently anti-competitive or monopolistic in nature; instead, they viewed these provisions as necessary tools for unions to effectively represent their members' interests.