In the United States v. Baltimore & Ohio Railroad Co., 1931, the U.S. Supreme Court ruled on a case involving interstate commerce and railroad rates for transporting goods across state lines. The federal government had sued the Baltimore & Ohio Railroad Company and other railroads, alleging that they were charging discriminatory rates to transport commodities from eastern states to St. Louis compared with similar shipments to Cincinnati or Louisville, thereby violating the Interstate Commerce Act of 1887 which prohibited unjustly preferential or prejudicial charges by carriers involved in interstate trade. The court held that while there was evidence of rate disparity between different destinations, it did not necessarily constitute discrimination under law as long as these differences could be justified based on legitimate factors such as market conditions or competition among carriers at various locations. Furthermore, it was emphasized that courts should defer to administrative agencies like Interstate Commerce Commission (ICC) when interpreting complex economic data related to rate structures due its expertise in this field unless their conclusions are unreasonable or unsupported by substantial evidence.

In the dissenting opinion for United States et al. v. Baltimore & Ohio Railroad Co. et al., Justice Stone argued that the Interstate Commerce Commission (ICC) had overstepped its authority by ordering railroads to stop charging shippers different rates based on their location, a practice known as "zone pricing". He believed that this was not an issue of discrimination or unfairness, but rather a legitimate business strategy used by railroads to remain competitive and profitable in various markets. Furthermore, he contended that it was not within the ICC's power to regulate such practices unless they were proven to be unjustly discriminatory or detrimental to commerce - which he did not believe zone pricing inherently was. In his view, any changes in rate structures should come from Congress itself rather than regulatory bodies like the ICC.