The U.S. Supreme Court case Railway Express Agency, Inc. et al v. New York in 1948 revolved around a city ordinance that prohibited advertisements on vehicles unless they were for the business of the vehicle's owner. The plaintiffs, who ran an advertising agency using trucks to display ads throughout the city, argued that this law violated their Fourteenth Amendment rights by discriminating against certain types of commercial speech without reasonable basis. However, the court upheld New York City’s ban on mobile billboards with a unanimous decision stating that it did not violate equal protection under law as guaranteed by the Fourteenth Amendment because it was based on rational grounds and served legitimate state interests such as traffic safety and aesthetics. The court reasoned that while both forms of advertisement could potentially distract drivers and pedestrians alike, those displayed on delivery trucks would be less distracting since they are more predictable due to their fixed nature compared to constantly changing billboard displays which can cause sudden distractions leading to accidents.

In the dissenting opinion for Railway Express Agency, Inc. et al. v. New York, Justice Jackson argued that the law in question was discriminatory and violated equal protection under the Fourteenth Amendment of the Constitution. He believed that there was no rational basis for allowing businesses to advertise their own products on vehicles they owned or controlled while prohibiting other companies from advertising on those same vehicles simply because they did not own them directly. This distinction seemed arbitrary and unfair to him as it favored certain types of business over others without any clear justification related to public safety or welfare concerns.