The Perma Life Mufflers, Inc. v. International Parts Corp case in 1967 revolved around antitrust laws and the issue of whether or not a party could be held liable for damages if they willingly participated in an illegal scheme that violated these laws. The plaintiffs, franchisees of Midas (operating under the name International Parts Corporation), alleged that Midas had engaged in anti-competitive practices by requiring them to only sell products supplied by Midas and at prices set by them. They claimed this constituted a violation of Section 1 of the Sherman Act which prohibits certain restrictive business practices including price fixing. The Supreme Court ruled in favor of Perma Life Mufflers, stating that even though they were partakers in the monopolistic conduct as franchisees, they were still victims who suffered from it and thus had standing to sue for treble damages under section 4 of Clayton Act - an act designed to supplement existing antitrust laws like Sherman Act. This ruling was significant because it expanded liability for antitrust violations beyond just those who are coerced into participating but also included willing participants if their participation resulted from economic necessity rather than free choice.

In the dissenting opinion for Perma Life Mufflers, Inc. v. International Parts Corp., Justice Harlan argued that the majority had incorrectly interpreted and applied antitrust laws to this case. He contended that these laws were designed to protect competition, not individual competitors who may be harmed by restrictive business practices. In his view, Midas's franchising system did not restrict competition but rather enhanced it by allowing a new competitor (Midas) to enter an already competitive market (the muffler industry). Furthermore, he disagreed with the majority's conclusion that Midas's franchise agreements constituted illegal tying arrangements under antitrust law because they did not force franchisees into unwanted purchases or limit their ability to buy products from other suppliers. Finally, he criticized the majority for creating uncertainty in commercial law by suggesting that any contractual provision could potentially violate antitrust laws if it was deemed "unreasonable" – a standard which he found too vague and subjective.