In the 1998 case of Patrick Knowles v. Iowa, the United States Supreme Court ruled that police officers cannot search a vehicle without a warrant once they have issued a citation for a minor traffic violation. The decision was based on an incident in which Patrick Knowles was stopped for speeding and subsequently had his car searched by an officer who found marijuana and drug paraphernalia. The state of Iowa argued that such searches were justified under its law allowing officers to conduct full-blown searches when issuing citations as opposed to arresting motorists for minor offenses. However, the Supreme Court disagreed with this argument stating it violated Fourth Amendment protections against unreasonable searches and seizures because there is no automatic authority given to police officers to conduct warrantless search after issuing traffic citation unless other circumstances justify such action.

The dissenting opinion in the case of Patrick Knowles v. Iowa, 1998 argued that the majority's decision to prohibit warrantless searches of vehicles following a traffic citation was an unnecessary restriction on police powers. The dissenters believed that such searches were reasonable under the Fourth Amendment and did not pose significant threats to individual privacy rights. They pointed out that law enforcement officers often have legitimate reasons for conducting these types of searches, including ensuring their own safety and preventing evidence destruction. Furthermore, they suggested that limiting this power could potentially hinder crime prevention efforts by reducing officers' ability to discover contraband or other illegal items during routine traffic stops.