Yes -- there are limits. A search warrant gives police permission to conduct a physical search of a certain location to look for specific items. The search may not extend outside the parameters specified in the search warrant itself. In order to apply for a search warrant, law enforcement must show probable cause based on information they have received from a reliable source or from their own first-hand observations. Search warrants must be signed by a judge. If police officers conduct a search without a legal search warrant, the search -- and anything obtained during the search -- is presumed to be unreasonable.