In the case of Cleveland, Cincinnati, Chicago and St. Louis Railway Company v. Porter in 1907, the U.S Supreme Court ruled on a dispute involving railway safety regulations. The plaintiff, Porter, was injured while working for the railroad company due to an alleged violation of a safety appliance law by his employer. He sued for damages under federal law which allowed employees to recover damages from their employers if they were injured as a result of their employer's negligence or violation of certain safety statutes. The main issue before the court was whether this federal statute preempted state laws that might otherwise limit or bar such recovery. The defendant argued that since Indiana (where the incident occurred) had its own set of laws governing employee injuries and compensation claims - including contributory negligence and assumption-of-risk defenses - these should apply instead. However, Justice David Brewer delivered an opinion stating that when it came to enforcing specific federal standards related to railway worker safety; state laws could not supersede them even if they conflicted with those standards. Therefore, any limitations imposed by Indiana's workers' compensation scheme did not apply in this instance because Congress intended its legislation to have nationwide effect regardless of individual states' policies.

In the dissenting opinion for Cleveland, Cincinnati, Chicago and St. Louis Railway Company v. Porter (1907), Justice Harlan argued that the majority's decision was inconsistent with previous rulings of the Court regarding similar cases involving railway companies' liability for injuries to their employees. He contended that under federal law, a railroad company is liable if an employee's injury results from negligence on part of any other employees while they are engaged in commerce between states. The majority held that because Mr. Porter had not been actively involved in interstate commerce at the time of his accident but merely preparing to do so, he could not claim damages under this law; however, Justice Harlan disagreed with this interpretation and believed it too narrow - arguing instead that preparation activities should be considered as part of interstate commerce itself.