Probable cause along with exigent circumstances may justify a search or entry without a warrant. 2 This is also known as the "emergency doctrine.A search warrant is needed whenever law enforcement officers want to conduct a search or seizure. The Fourth Amendment, however, is not a guarantee against all searches and seizures, but only those that are deemed unreasonable under the law. Typically, law enforcement does need a warrant to perform a search and seizure that does not violate your Fourth Amendment rights. Not without a search warrant. The Constitution and 4th Amendment protects many types of unreasonable searches and seizures, however, it does not protect against things left out on the open. The Fourth Amendment requires that the warrant be specific about the place to be searched and items to be seized. It is an exception to the warrant requirement. If a person gives police permission to search, then police can search without either a warrant or probable cause.