The Fourth Amendment protects people against "unreasonable searches and seizures. The Fourth Amendment places limits on the power of the police to detain and search people.This helps to protect Americans' privacy and freedom. The Fourth Amendment establishes constitutional limits on police power. 106. Like. 1. Probable Cause: The 4th Amendment requires that law enforcement officers have probable cause or reasonable suspicion to initiate a traffic stop. The Fourth Amendment requires the government to obtain a warrant based on probable cause to conduct a legal search and seizure. The Fourth Amendment to the United States Constitution protects us from unlawful governmental intrusion. It protects our persons, places, and things. The rule in a warrantless search of premises. The rule apparently never applied in case of a search of the person.