In the case Cantor v. Detroit Edison Co., the Supreme Court ruled in 1975 that a light bulb exchange program run by Detroit Edison, a privately owned public utility company, was subject to federal antitrust laws. The program provided free light bulbs to its electricity customers as part of their service agreement. Selden Drugs Co., a small business selling light bulbs among other items, argued this constituted unfair competition and violated the Sherman Antitrust Act because it used monopoly power to stifle competition in another market (light bulb sales). The court agreed with Selden Drugs Co., rejecting Detroit Edison's argument that state regulation exempted them from federal antitrust law under Parker v. Brown (1943), which held states could impose anti-competitive restrictions on businesses without violating federal law if they were acting within their sovereign capacity.

In the dissenting opinion for Cantor v. Detroit Edison Co., Justice Brennan, joined by Justices Douglas and Marshall, argued that the majority's decision to uphold a light bulb exchange program as part of regulated utility rates was incorrect. They contended that this ruling ignored previous court decisions which held that state-sanctioned monopolies should not be allowed to use their power to compete in other markets. The dissenters believed that Detroit Edison used its monopoly over electricity supply to unfairly dominate the market for light bulbs, disadvantaging competitors like Selden Drugs Co. Furthermore, they disagreed with the majority's view on antitrust immunity for public utilities; while acknowledging some exceptions may exist due to regulatory structures or compelling interests, they maintained these were narrow and did not apply here. Thus, they concluded that federal antitrust laws should have been enforced against Detroit Edison’s practices.