In the 1940 case of New York, Chicago & St. Louis Railroad Co. v. Frank, the United States Supreme Court ruled in favor of the railroad company and against a former employee who had been injured on the job. The plaintiff, Mr. Frank, was an interstate commerce worker for the railroad company when he sustained injuries due to negligence by his employer which led him to file a lawsuit under Federal Employers' Liability Act (FELA). However, at that time he was not engaged in interstate commerce duties but rather intrastate activities - repairing tracks within one state only - thus making FELA non-applicable according to its terms as interpreted by courts then. The court held that since Mr.Frank's work during injury did not directly or closely relate to interstate transportation despite being generally employed as an interstate worker; hence it fell outside FELA’s purview thereby exempting his employer from liability under this act. This decision established precedent regarding how federal laws like FELA apply depending upon whether workers are performing tasks related specifically to their designated roles involving interstate commerce at time of any incident causing harm.

In the dissenting opinion for NEW YORK, CHICAGO & ST. LOUIS RAILROAD CO. v. FRANK (1940), Justice Frankfurter disagreed with the majority's interpretation of federal law and its application to state laws regarding negligence in railroad accidents. He argued that Congress did not intend to preempt all state laws on this issue when it passed the Federal Employers' Liability Act (FELA). Instead, he believed that FELA was designed to supplement existing state laws by providing an additional avenue for injured workers to seek compensation from their employers under certain circumstances. Therefore, he contended that states should still be allowed to enforce their own negligence laws alongside FELA unless there is a direct conflict between them which cannot be reconciled through reasonable interpretation or accommodation.