In the case of Maryland v. Macon, 1984, the U.S. Supreme Court ruled that a police officer's purchase of obscene material from an adult bookstore did not constitute a search under the Fourth Amendment. The defendant, Macon, was convicted for selling obscene materials after an undercover detective purchased two magazines from his store and later returned with a warrant to seize other items based on their content. On appeal, Macon argued that the initial purchase constituted an illegal search because it was conducted without a warrant and therefore violated his Fourth Amendment rights against unreasonable searches and seizures. However, in its decision delivered by Justice Byron White (with Justices William Brennan Jr., Thurgood Marshall dissenting), the court held that no such violation had occurred as there was no forced entry into private premises or seizure of goods not voluntarily offered for sale.

In the dissenting opinion for Maryland v. Macon, Justice Brennan disagreed with the majority's interpretation of what constitutes a search under Fourth Amendment law. He argued that when an undercover officer purchased allegedly obscene materials from an adult bookstore and later returned to arrest the clerk, it constituted as a warrantless search and seizure in violation of the Fourth Amendment rights. According to him, this was not merely observation in plain view but rather involved physical intrusion into personal property without consent or warrant which should be considered unconstitutional unless justified by exigent circumstances or probable cause. The majority’s decision failed to recognize this distinction thereby undermining constitutional protections against unreasonable searches and seizures.