Police entrance into rooming house common areas, using a key to gain entry.

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Can police in Maryland enter A locked Apartment/Rooming house where a common hallway kitchen and bathroom are present however they are utilized by tenants of the various apartments. Each tenant is supplied with a key to the house and a key to their room. The landlord supplied a key to the police advising them they can make entry to the common area's of the apartment to inspect and make sure there are no trespassers. Please provide any known federal and state case law.