The Pennsylvania Public Utility Commission v. Pennsylvania Railroad Co., 1965, was a case that dealt with the issue of whether or not the state could regulate interstate commerce by imposing restrictions on railroad rates for intrastate travel. The Supreme Court ruled in favor of the Pennsylvania Railroad Company, stating that states cannot interfere with interstate commerce and therefore cannot impose regulations on railroads operating across state lines. This decision upheld the supremacy of federal law over state law when it comes to regulating interstate commerce as per Commerce Clause of U.S Constitution. It also emphasized that any attempt by a State to establish its own policy regarding such matters would disrupt and obstruct national uniformity in this field which is necessary for national interests.

In the dissenting opinion for Pennsylvania Public Utility Commission v. Pennsylvania Railroad Co., Justice Harlan argued that the majority's decision was a departure from established principles of federalism and administrative law. He contended that it was inappropriate for the Supreme Court to intervene in matters traditionally left to state regulatory agencies, such as setting railroad rates. According to him, there should be deference given to these agencies' expertise and their role in protecting public interests within their jurisdictional boundaries. Furthermore, he disagreed with the majority's interpretation of relevant statutes, asserting they did not provide clear authorization for this type of judicial intervention into state affairs. Therefore, he believed that by overruling decisions made by both a state commission and court without sufficient legal basis or compelling reasons related to national policy or constitutional rights infringed upon states' rights and disrupted delicate balances between different levels of government.