In the case of Semler v. Oregon State Board of Dental Examiners et al., 1934, Dr. Frank G. Semler challenged a law in Oregon that prohibited advertising by dentists as unconstitutional under the Fourteenth Amendment's Due Process Clause and Equal Protection Clause. The Supreme Court upheld the state law, ruling that it was within a state's police power to regulate professional conduct including advertising practices for professions such as dentistry or medicine to protect public health and welfare from deceptive practices. The court found no violation of equal protection since all practitioners were treated equally under this regulation, nor did they find any deprivation of property without due process because there was no inherent right to advertise one’s profession in whatever manner desired.

In the dissenting opinion for Semler v. Oregon State Board of Dental Examiners, Justice McReynolds disagreed with the majority's upholding of an Oregon law that restricted dental advertising. He argued that this was a violation of due process under the Fourteenth Amendment because it interfered with a dentist's right to conduct business. According to him, there was no evidence showing that such restrictions were necessary for public health or safety and therefore should not be upheld as valid exercises of police power by states. He also pointed out inconsistencies in how different professions were treated under similar laws, suggesting unequal protection under the law.