In the 1936 case of The Pep Boys, Manny, Moe & Jack of California, Inc. v. Pyroil Sales Co., Inc., the U.S Supreme Court was tasked with resolving a dispute over trademark infringement and unfair competition. The Pep Boys had been using their name in business since 1921 while Pyroil started using 'Pep' in its branding from 1930 onwards for similar automotive products and services which led to confusion among customers. The court ruled that even though both companies were operating in different states (The Pep Boys primarily on the West Coast and Pyroil on East), there was still an overlap due to advertising efforts reaching consumers nationwide causing potential damage to reputation or sales for either company because of mistaken identity by consumers. Therefore, it held that such use constituted trademark infringement and unfair competition under federal law despite geographic separation between businesses.

The dissenting opinion in the case of The Pep Boys, Manny, Moe & Jack of California, Inc. v. Pyroil Sales Co., Inc., argued that the majority's decision to uphold a lower court ruling against Pep Boys was incorrect due to an improper interpretation of trademark law and unfair competition principles. They contended that there was no evidence showing consumers were likely to be confused between the two companies' products or services based on their respective trademarks. Furthermore, they disagreed with the majority's view about "secondary meaning," arguing it should not apply because both companies used common words in their names which could not be exclusively owned by one party under trademark law. The dissent also criticized how damages were calculated and awarded without sufficient proof of actual harm suffered by Pyroil Sales Co., Inc.