In the case of Leishman v. Associated Wholesale Electric Co., 1942, the United States Supreme Court was tasked with deciding on a matter related to patent infringement. The plaintiff, Leishman, held patents for an electrical transformer and accused Associated Wholesale Electric Co. of infringing upon his rights by manufacturing similar transformers without permission or license. However, the defendant argued that they had not infringed on any patents as their product was based on prior art - meaning it used technology or designs already available in public domain before Leishman's patent application date. The lower courts ruled in favor of the defendant but this decision was appealed to the Supreme Court which reversed it and remanded for further proceedings consistent with its opinion. The court found that there were factual issues regarding whether certain elements of prior art cited by defendants were equivalent to those claimed in plaintiff’s patents; these should have been resolved at trial rather than being decided as a matter of law by summary judgment.

In the dissenting opinion for Leishman v. Associated Wholesale Electric Co., Justice Frank Murphy argued that the majority's decision to uphold a state law restricting out-of-state corporations from doing business in Utah without consent was unconstitutional. He contended that this law violated the Commerce Clause of the U.S. Constitution, which gives Congress exclusive power over interstate commerce. According to him, allowing states to impose such restrictions would lead to economic protectionism and hinder free trade among states, thereby undermining national unity and prosperity. Furthermore, he disagreed with the majority's view that upholding this law served public interest as it could potentially protect local businesses from unfair competition by larger out-of-state companies; instead he believed it only served parochial interests at expense of broader national interests.