When the police want to go through your property and belongings, they will need a search warrant, which is an official document executed by a judge that gives officers the right to go through your stuff. In order to get a search warrant, the officers must have probable cause to believe criminal activity has, is, or will be taking place.
A search warrant will list items and/ or locations that can be sifted through by the officers. The officers may not search locations that are not listed. For example, if the warrant specifies only the kitchen and living room of a home, the officer cannot search the bedrooms. The warrant also allows the officers to seize items during their search.
Search warrants are not needed if you give consent to the officer to search. They are also not needed after an arrest when the officer searches the arrestee and the surrounding area.
If your loved one has been arrested, and an officer comes to you because you are very close with the arrestee and wishes to search your property and belongings, you can say no. They would have to come back with a warrant.