In Grand Trunk Railway Company v. Cummings, the Supreme Court of the United States was asked to decide whether a state court had the authority to enjoin a railroad company from operating its trains in a manner that was deemed to be dangerous. The plaintiff, Cummings, had been injured when a train operated by the defendant, Grand Trunk Railway Company, had collided with another train. Cummings argued that the defendant had been negligent in its operation of the train, and that the state court had the authority to enjoin the defendant from operating its trains in a manner that was deemed to be dangerous. The Supreme Court held that the state court did not have the authority to enjoin the defendant from operating its trains in a manner that was deemed to be dangerous. The Court reasoned that the power to regulate the operation of railroads was vested in the federal government, and that the state court did not have the authority to interfere with the federal government's power to regulate the operation of railroads. The Court further held that the state court could not enjoin the defendant from operating its trains in a manner that was deemed to be dangerous, as this would be an interference with the federal government's power to regulate the operation of railroads. In conclusion, the Supreme Court held that the state court did not have the authority to enjoin the defendant from operating its trains in a manner that was deemed to be dangerous. The Court reasoned that the power to regulate the operation of railroads was vested in the federal government, and that the state court did not have the authority to interfere with the federal government's power to regulate the operation of railroads.

Justice Field delivered the dissenting opinion in Grand Trunk Railway Company v. Cummings, arguing that the majority's decision was wrongfully decided and should be reversed. He argued that a contract between two parties is binding on them both, regardless of any state laws or regulations which may conflict with it. The contract at issue here provided for payment to Cummings by Grand Trunk Railway Company (GTRC) in Canadian currency; however, Michigan law prohibited such payments from being made in foreign currency without prior approval from its legislature. Justice Field asserted that this law did not apply to GTRC because it had been incorporated under federal law and thus could only be regulated by Congress - not Michigan's legislature - as per Article I Section 8 of the Constitution. Furthermore, he noted that even if GTRC were subject to regulation by Michigan’s legislature, they would still have no authority over contracts already entered into before their enactment of said legislation prohibiting payments in foreign currencies unless those contracts expressly stated otherwise – which this one did not do so therefore making it invalid according to established legal principles regarding contractual obligations between two parties