The Second Employers' Liability Cases, also known as Mondou v. New York, New Haven & Hartford Railroad Co., was a U.S Supreme Court case in 1911 that dealt with the issue of federal jurisdiction over state workers' compensation laws. The plaintiff, Mondou, an employee of the defendant railroad company had been injured while working and sought to recover damages under the Federal Employers’ Liability Act (FELA). The defendant argued that FELA was unconstitutional because it infringed upon states' rights to regulate their own internal affairs. However, the Supreme Court ruled in favor of Mondou stating that Congress has power under Commerce Clause to regulate liability of interstate carriers for injuries suffered by their employees during course of employment. This decision established a precedent allowing federal law to supersede state law when dealing with issues related to interstate commerce.

In the dissenting opinion for Mondou v. New York, New Haven & Hartford Railroad Co., Justice Oliver Wendell Holmes Jr. argued that Congress had overstepped its constitutional authority by passing the Federal Employers Liability Act (FELA). He contended that FELA was not a valid exercise of Congress's power to regulate interstate commerce because it applied to all railroad employees, regardless of whether their work directly involved interstate commerce. Furthermore, he believed that this broad application infringed upon states' rights to govern local matters and created an unnecessary federal jurisdiction in cases involving personal injuries sustained by railroad workers. In his view, such cases should be handled at the state level unless they specifically involve issues related to interstate commerce.