The U.S. Supreme Court case Atchison, Topeka & Santa Fe Ry. Co. v. United States in 1925 revolved around the interpretation of the Interstate Commerce Act and its application to railroad companies' freight rates for transporting goods across state lines. The Atchison, Topeka & Santa Fe Railway Company challenged an order by the Interstate Commerce Commission (ICC) that reduced their established rates on certain commodities transported from Gulf ports to points in Arizona and New Mexico, arguing it was unjustly low and confiscatory in nature violating due process clause of Fifth Amendment rights. However, the Supreme Court upheld ICC's decision stating that while courts can determine whether a rate is so low as to be confiscatory and thus unlawful under due process clause; they cannot decide what would be a reasonable rate within lawful limits which is purely administrative function vested with ICC by Congress under Interstate Commerce Act. Therefore, even though some justices dissented believing that court should have power to review reasonableness of rates set by ICC; majority opinion held firm asserting separation of powers between judiciary reviewing legality versus administrative agencies determining policy matters like setting reasonable rates within legal bounds.

In the dissenting opinion for Atchison, Topeka & Santa Fe Ry. Co. v. United States, Justice McReynolds disagreed with the majority's interpretation of the Hepburn Act and its application to this case. He argued that Congress did not intend to prohibit all free transportation services but only those which could potentially lead to preferential treatment or discrimination among shippers. According to him, providing free carriage for federal troops during World War I was a patriotic act rather than an unfair practice as it didn't result in any unjust preference or advantage over other customers since everyone else was also transported without charge under similar circumstances due to wartime exigencies. Therefore, he believed that such actions should be exempted from regulatory penalties imposed by Interstate Commerce Commission (ICC). Furthermore, he criticized ICC's decision as arbitrary and inconsistent because they had previously allowed railroads to provide free transportations under certain conditions without considering them illegal rebates or concessions.