The United States Supreme Court case, UNITED STATES v. DIAMOND COAL & COKE COMPANY in 1920 revolved around the issue of whether a coal company was liable for taxes on profits made from selling its own mined coal. The Diamond Coal and Coke Company argued that it should not be taxed because the tax law at the time only applied to companies who bought and sold coal, not those who mined and sold their own product. However, the government contended that since Diamond Coal both produced and sold coal, they were effectively acting as both producer and dealer; thus making them subject to taxation under existing laws. The Supreme Court ruled in favor of the U.S Government stating that even though Diamond Coal did mine its own product, by selling it directly to consumers they acted as dealers too which brought them within scope of taxable entities according to Revenue Act of 1918. Therefore, they were required to pay taxes on their profits from these sales.

The dissenting opinion in the United States v. Diamond Coal & Coke Company case argued that the government had no right to impose penalties on a company for violating anti-trust laws if it was not explicitly proven that their actions directly restrained trade or commerce. The justice believed that while the Sherman Act intended to prevent monopolies and protect competition, its application should be limited to clear cases of restraint or monopoly. In this particular case, he felt there wasn't enough evidence proving Diamond Coal & Coke Company's acquisition of land and coal rights significantly impacted interstate commerce or created a monopoly situation. Therefore, he disagreed with penalizing them based on assumptions rather than concrete proof of violation.