The U.S. Supreme Court case Walling, Wage and Hour Administrator v. Nashville, Chattanooga & St. Louis Railway in 1946 revolved around the interpretation of the Fair Labor Standards Act (FLSA) as it pertained to railway workers who were engaged in both interstate and intrastate commerce activities within a single workweek. The court had to decide whether these employees should be paid overtime for hours worked beyond forty per week under FLSA provisions or if they fell under an exemption due to their involvement with interstate commerce which was regulated by another law - the Interstate Commerce Act (ICA). The Supreme Court ruled that such mixed-activity employees are not exempt from FLSA's overtime pay requirements even though some of their duties involve interstate commerce operations governed by ICA regulations. This decision clarified that federal labor laws intended to protect worker rights apply broadly unless specific exemptions are clearly established.

In the dissenting opinion for Walling v. Nashville, Chattanooga & St. Louis Railway, Justice Frankfurter argued that the majority's interpretation of the Fair Labor Standards Act was incorrect and overly broad. He contended that Congress did not intend to include all employees involved in commerce within its scope but rather only those directly engaged in producing goods for commerce or closely related processes or occupations. The justice believed that this narrower interpretation would better align with Congress's intent and avoid unnecessary federal intrusion into areas traditionally regulated by states such as local transportation services. Furthermore, he expressed concern about potential negative impacts on businesses due to increased labor costs resulting from a broader application of wage and hour regulations under the act.