Oliver Wendell Holmes, Jr.

“ It would be a tax upon the railroad when the company wished to run a mail train wholly made up of mail cars, but it could be done and it is not necessary to say that the State could not require it. But when the United States has exercised its exclusive powers over interstate commerce so far as to take possession of the field, the States no more can supplement its requirements than they can annul them. ”

“ We pass to the merits of the case. If all that had been done on behalf of the United States in the way of regulation had been to determine how mail cars should be built, and to exclude a thirty-inch platform, it might be said that the state law could be obeyed by putting a different car at the end of the train. ”

“ The Railroad Company appealed to the Superior Court, setting up that the order violated the commerce clause of the Constitution (Art. 1, § 8) and that in view of the federal legislation and rules, including the order of the Interstate Commerce Commission dated March 13, 1911, and made under the Safety Appliance Act (Act March 2, 1893, c. 196, 27 Stat. 531 [Comp. St. §§ 8605-8612] ) , and other matters referred to, the State Commission had no power to do what it did. ”