In the case of Seaboard Air Line Railway v. Horton (1915), the U.S Supreme Court ruled in favor of Seaboard Air Line Railway, reversing a decision by the Georgia Supreme Court. The dispute arose when Mr. Horton was injured while working for the railway company and sought compensation under Georgia's Employer’s Liability Act. However, this state law conflicted with federal laws governing interstate commerce, which included railroad operations like those conducted by Seaboard Air Line Railway. The court held that since railroads are instrumentalities of interstate commerce, they fall within exclusive federal jurisdiction and cannot be subjected to conflicting state regulations or liability rules without congressional approval. Therefore, it concluded that Georgia's Employer’s Liability Act could not apply to injuries sustained during interstate transportation activities on railroads. This ruling reinforced the principle of federal supremacy over states in matters related to interstate commerce and highlighted how conflicts between state and federal laws should be resolved in favor of national uniformity.

The dissenting opinion in the case of Seaboard Air Line Railway v. Horton argued that the majority's decision to uphold a state law requiring railroads to provide equal accommodations for black and white passengers was incorrect. The dissenters believed this ruling violated the Commerce Clause of the U.S Constitution, which gives Congress exclusive power over interstate commerce. They contended that by upholding such a law, it would allow individual states to regulate interstate commerce, thereby undermining federal authority and creating potential inconsistencies between states' laws governing railway operations. Furthermore, they asserted that there was no evidence showing any substantial local interest being served by enforcing racial segregation on trains crossing state lines; thus it could not be justified as an exercise of police powers reserved for states under Tenth Amendment.