In Parsons v. Chicago and Northwestern Railway Company, the U.S Supreme Court ruled in favor of the railway company, dismissing a claim by Parsons for damages incurred due to negligence on part of the railway company. The case arose when Mr. Parsons' horses were killed after they strayed onto an unfenced portion of the railroad's track. He argued that under Iowa law, which required railroads to fence their tracks or be held liable for livestock deaths, he was entitled to compensation from the railroad company. However, it was found that at this particular location where his horses had wandered onto - a bridge over a public highway - fencing would have been impractical and dangerous as it could obstruct visibility for trains approaching crossings or stations. The court therefore concluded that while general laws requiring fences along railways are valid exercises of police power intended to protect property owners adjacent to such lines; these laws should not apply universally without considering practicality and safety concerns associated with specific locations like bridges over highways.

In the dissenting opinion for Parsons v. Chicago and Northwestern Railway Company, it was argued that the majority's decision to uphold a state law regulating railroad rates violated principles of federalism by infringing on powers reserved for Congress under the Commerce Clause of the U.S. Constitution. The dissent maintained that railroads were instrumentalities of interstate commerce and thus should be subject to federal rather than state regulation. It also contended that allowing states to regulate railroad rates could lead to inconsistent regulations across different states, creating confusion and inefficiency in interstate commerce operations. Furthermore, it suggested that such regulation might unfairly burden railroads with excessive costs or restrictions, potentially undermining their financial stability and ability to provide essential transportation services.