In the 1908 case of Siler et al., Constituting The Railroad Commission of Kentucky, v. Louisville and Nashville Railroad Company, the U.S Supreme Court ruled in favor of the railroad company. The dispute arose when the state commission attempted to enforce a law that required railroads to provide separate but equal accommodations for black and white passengers within their trains. However, this was in conflict with federal laws which prohibited racial segregation on interstate carriers under Interstate Commerce Act regulations. The court held that while states have power over local matters concerning railroads operating within their boundaries, they cannot impose rules or regulations contradicting federal laws governing interstate commerce - such as those prohibiting racial segregation on interstate carriers - because these are exclusively under federal jurisdiction according to Constitution's Supremacy Clause.

In the dissenting opinion for Siler et al., Constituting The Railroad Commission of Kentucky, v. Louisville and Nashville Railroad Company, Justice Harlan disagreed with the majority's decision to uphold a federal court injunction against state railroad regulations. He argued that this case was not about whether Congress had authority over interstate commerce but rather if it had exercised such power in a way that precluded states from protecting their citizens' welfare. According to him, there was no explicit or implicit congressional action preventing states from regulating local aspects of railroads even though they were involved in interstate commerce. Therefore, he believed the Court should have allowed Kentucky's regulation on intrastate rates as long as it did not interfere with national uniformity or burden interstate commerce excessively. Furthermore, he criticized his colleagues for ignoring principles of federalism by allowing federal courts to intervene prematurely without letting state courts interpret their own laws first.