Ex parte Railroad Company is a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue an injunction against a railroad company. The case arose when the state of Missouri sought to enjoin the St. Louis & Iron Mountain Railroad Company from operating its trains on a certain stretch of track. The state argued that the railroad was operating in violation of a state law that prohibited the operation of trains on certain tracks without the consent of the state. The Supreme Court held that the state court did not have the authority to issue the injunction. The Court reasoned that the state law was preempted by the federal law that granted the railroad the right to operate its trains on the track in question. The Court further held that the state court was not authorized to interfere with the railroad's operations, as the federal law granted exclusive authority to the federal government to regulate interstate commerce. The Court's decision in Ex parte Railroad Company established the principle that state courts cannot interfere with the operations of a railroad that is operating in accordance with federal law. This decision has been cited in numerous subsequent cases involving the regulation of interstate commerce.

In Ex Parte Railroad Company, the Supreme Court was asked to decide whether a railroad company could be held liable for damages caused by its negligence. The majority opinion of the court found that while the company had acted negligently, it did not owe any damages because there was no contract between them and those affected by their actions. Justice Field dissented from this decision, arguing that even without a contract in place, companies should still be held accountable for their negligent behavior. He argued that if companies were allowed to escape liability simply because they lacked an agreement with those injured by their negligence then they would have little incentive to act responsibly or take safety precautions when operating dangerous machinery like trains. Furthermore, he noted that allowing such behavior would create an unjust situation where victims of corporate wrongdoing are left uncompensated despite having suffered real losses due to another's carelessness.