Ex parte Railway 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 railway company. The case arose when the state of Missouri sought to enjoin the St. Louis and Iron Mountain Railway Company from operating its trains on a certain stretch of track. The state argued that the railway company had failed to comply with certain state laws and regulations, and that the injunction was necessary to protect the public safety. The Supreme Court held that the state court did not have the authority to issue the injunction. The Court reasoned that the state court lacked jurisdiction over the railway company, as the company was a federally chartered corporation. The Court further held that the state court could not interfere with the federal government's exclusive power to regulate interstate commerce. The Court concluded that the state court's injunction was invalid and must be set aside. The decision in Ex parte Railway Company established the principle that state courts cannot interfere with the federal government's exclusive power to regulate interstate commerce. This principle has been applied in numerous cases since then, and remains an important part of the law today.

In Ex Parte Railway Company, the Supreme Court was asked to decide whether a state court had jurisdiction over an interstate railway company. The majority opinion held that the state court did not have jurisdiction and that only federal courts could hear cases involving interstate railroads. Justice Field dissented from this decision, arguing that states should be allowed to exercise their authority in matters concerning intrastate commerce. He argued that Congress had never intended for all railroad-related disputes to be heard exclusively by federal courts and noted that allowing states to adjudicate such matters would help ensure uniformity of laws across different jurisdictions. Furthermore, he argued it was unfair for one party involved in a dispute with an interstate railroad company—in this case, the plaintiff—to have no recourse but to bring suit in a distant federal court when they were unable or unwilling to do so due financial constraints or other reasons. In conclusion, Justice Field believed it was within the power of each state's legislature and judiciary system determine how best handle disputes between its citizens and out-of-state corporations operating within its borders