In the Montana Railway Company v. Warren case of 1890, the U.S Supreme Court ruled in favor of Montana Railway Company. The dispute arose when Warren sued for damages after his cattle were killed by a train operated by the railway company. He claimed that it was due to negligence on part of the company as they failed to sound their whistle or ring their bell while approaching a public highway crossing where his cattle were grazing nearby. However, there was no statutory requirement in place at that time mandating railways to use such signals at crossings within state boundaries. The court held that even though sounding whistles and ringing bells are generally accepted precautions taken by trains near crossings, absence of these actions does not necessarily constitute negligence if there is no legal obligation requiring them to do so. Therefore, since there was no law compelling railroads operating within Montana's borders to signal their approach at public highway crossings during this period, failure on part of Montana Railway Company did not amount to neglectful conduct.

In the dissenting opinion for Montana Railway Company v. Warren, Justice Lamar disagreed with the majority's ruling that a state could regulate rates charged by railway companies. He argued that such regulation violated the Commerce Clause of the U.S. Constitution, which gives Congress exclusive power to regulate interstate commerce. According to him, railroads were instruments of interstate commerce and therefore should be free from state interference in their operations or pricing structures. Furthermore, he contended that allowing states to control railroad rates would lead to inconsistencies and conflicts between different states' regulations - potentially disrupting national trade patterns and undermining federal authority over interstate commerce.