In the case of Keller et al., constituting the Public Utilities Commission of the District of Columbia, v. Potomac Electric Power Company et al., 1922, the Supreme Court ruled on a dispute between a public utilities commission and an electric power company over rate setting. The court held that while regulatory bodies have broad powers to set rates for public utilities, these rates must be reasonable and cannot result in confiscation of property. This means that regulators cannot set rates so low as to prevent utility companies from earning a fair return on their investments. In this particular case, it was determined that the regulator had not provided sufficient evidence or reasoning to justify its proposed rate reductions for Potomac Electric Power Company (PEPCO). Therefore, PEPCO's due process rights under Fifth Amendment were violated by imposing such low rates without proper justification.

In the dissenting opinion for Keller et al. v. Potomac Electric Power Company et al., Justice McReynolds disagreed with the majority's decision to uphold a rate increase granted by the Public Utilities Commission of D.C. to Potomac Electric Power Company (PEPCO). He argued that PEPCO had not demonstrated sufficient need for an increased return on its investment, and thus, it was unjustified in raising rates for consumers. Furthermore, he contended that there were no extraordinary circumstances warranting such an increase and criticized the majority's reliance on mere possibilities or potential future conditions rather than concrete evidence presented at trial. Ultimately, Justice McReynolds believed that this case represented a dangerous precedent where utility companies could arbitrarily raise their rates without adequate justification or oversight from regulatory bodies.