Originally Posted by NALEM

Not sure about all US States but in California the law is clear. The landlord trespassed.

As a property owner myself I have walked in without advance notice (on tenants I suspect are sub letting, damaging the property, etc). All my agreements clearly state that I am not renting the entire unit, but sharing the place. It is structured to recognize me as a roommate/flat mate.

I only inspect the common areas (hallway, guest bathrooms, hallway closets, kitchen, living and dining room) and "look" but never walk into any of the bedrooms if the doors are closed.