In the case of Siler et al., as Railroad Commission, v. Illinois Central Railroad Company (1908), the U.S. Supreme Court dealt with a dispute over railroad freight rates in Kentucky. The state's railroad commission had set maximum rates that railroads could charge for transporting goods within the state, and these were challenged by the Illinois Central Railroad Company on grounds that they violated federal law and its constitutional rights to due process and equal protection under Fourteenth Amendment. The court ruled in favor of Illinois Central, holding that while states have power to regulate commerce within their borders, such regulations must not conflict with federal laws or violate constitutional protections afforded to corporations as persons under Fourteenth Amendment. This decision affirmed supremacy of federal law over conflicting state regulations and reinforced corporate personhood doctrine.

In the dissenting opinion for Siler et al., as Railroad Commission, v. Illinois Central Railroad Company, Justice Harlan argued that the majority erred in its interpretation of Kentucky law and overstepped its jurisdiction by deciding on a state issue. He contended that it was not within the Supreme Court's power to interpret or apply state laws when there is no federal question involved. Furthermore, he believed that if a case could be decided on either federal or state grounds, then it should be resolved based on state law alone without considering any constitutional questions. In this case, he felt that the court had unnecessarily reached out to decide a constitutional question about rate regulation under Kentucky law instead of leaving it up to local authorities who are more familiar with their own regulations and conditions.