In the 1957 case of McKinney v. Missouri-Kansas-Texas Railroad Co., the U.S. Supreme Court ruled in favor of the railroad company, reversing a decision by the Kansas Supreme Court that had awarded damages to an injured worker, William McKinney. The court held that under federal law (the Federal Employers' Liability Act), it was not sufficient for a plaintiff to show only that his injury could have been caused by employer negligence; he must prove it was indeed caused by such negligence. In this case, there were multiple possible causes for McKinney's injuries and he failed to provide enough evidence proving his injuries were directly due to his employer’s negligence.

In the dissenting opinion for McKinney v. Missouri-Kansas-Texas Railroad Co., it was argued that the majority's decision to uphold a state law requiring railroads to maintain fences along their tracks, even in urban areas, was an unjustifiable burden on interstate commerce. The dissenters believed that this requirement did not serve any legitimate public safety purpose and instead imposed unnecessary costs on railroad companies engaged in interstate trade. They contended that such laws should be subject to scrutiny under the Commerce Clause of the U.S Constitution, which gives Congress exclusive power over interstate commerce. By upholding this law without considering its impact on interstate trade, they felt that the court had failed to protect federal interests from undue interference by states.