In the case of REA v. United States, 1955, the Railway Express Agency (REA) challenged a New York City ordinance that prohibited advertisements on vehicles unless they were for the business services provided by said vehicle. The Supreme Court upheld this law as constitutional and not in violation of equal protection under the Fourteenth Amendment. The court ruled that it was reasonable for New York to decide that such advertising could distract drivers and potentially cause accidents. It also found no issue with exempting vehicle owners who advertised their own goods or services because these ads would likely be less distracting due to their relevance to what was being transported in those vehicles. This decision reinforced states' rights to regulate commercial speech based on public safety concerns without violating businesses' right to equal protection under law.

The dissenting opinion in the case of REA v. United States argued that the majority's decision was a misinterpretation of the Interstate Commerce Act and its amendments. The dissenters believed that Congress intended to regulate, not prohibit, rebates and other discriminatory practices by railroads. They contended that if Congress had wanted to outlaw all forms of price discrimination, it would have done so explicitly in clear language rather than through vague terms like "unjust" or "unreasonable." Furthermore, they pointed out inconsistencies within the majority's interpretation; while some types of price differences were deemed illegal under their reading of the law, others were inexplicably allowed to continue. Finally, they warned against judicial overreach and urged respect for legislative intent.