In the case of Preston v. United States in 1963, the U.S Supreme Court ruled that a warrantless search of a vehicle after its occupants had been arrested and removed from the scene was not justifiable as an incident to their arrest. The defendants were initially arrested for vagrancy but later charged with conspiracy to rob a bank based on evidence found during this subsequent search. The court held that once suspects have been taken into custody and removed from their vehicle, there is no longer any danger they might access weapons or destroy evidence within it - thus eliminating two key exceptions to the Fourth Amendment's requirement for law enforcement officers to obtain warrants before conducting searches. Therefore, police should have obtained a warrant before searching Preston’s car post-arrest because it was not immediately related to his arrest nor did exigent circumstances exist at that time.

In the dissenting opinion for Preston v. United States, Justice Clark argued that the majority's decision to suppress evidence obtained from a warrantless search of a vehicle after arrest was inconsistent with previous rulings and could potentially hinder law enforcement efforts. He pointed out that in past cases, such as Brinegar v. United States and Carroll v. United States, the Court had upheld similar searches under what is known as the "automobile exception" to the Fourth Amendment's requirement for a warrant due to vehicles' inherent mobility and lower expectation of privacy compared to homes or offices. Furthermore, he contended that there were no signs of police misconduct or bad faith in this case; rather, they acted based on reasonable suspicion following standard procedures at that time which included impounding cars used in crimes until trial completion.