The case of New York, New Haven & Hartford Railroad Company v. United States in 1921 revolved around the issue of whether or not the Interstate Commerce Commission (ICC) had overstepped its authority by ordering a railroad company to cease certain practices that were deemed discriminatory and unfair. The ICC argued that the railroad company was giving preferential treatment to one shipper over another by providing lower rates for transporting goods. The Supreme Court ruled in favor of the ICC, stating that it did indeed have jurisdiction under federal law to regulate such matters and prevent unjust discrimination among shippers. This decision reinforced the power of regulatory agencies like the ICC, affirming their role in ensuring fair business practices within industries they oversee.

In the dissenting opinion for New York, New Haven & Hartford Railroad Company v. United States, Justice McReynolds disagreed with the majority's interpretation of the Interstate Commerce Act. He argued that Congress did not intend to give such broad powers to the Interstate Commerce Commission (ICC) as interpreted by his colleagues in their ruling. According to him, if Congress had intended for ICC to have authority over intrastate rates affecting interstate commerce, it would have explicitly stated so in clear terms within the legislation itself. Furthermore, he pointed out that this decision could potentially lead to a dangerous concentration of power and regulatory control within one federal agency - an outcome which was never contemplated or desired by lawmakers when they enacted this law.