Legal Question in Real Estate Law in California

Re: door locks

It's not a crime per se, but if the purpose or effect is to hinder the landlord's right of inspection or duty to maintain, it could be a trespass or a breach of the rental agreement. My advice is don't do it unless in a genuine emergency or without the landlord's permission, and be sure to provide the landlord with a key.

Re: door locks

No, it is not a crime, but if your landlord requests a copy of the key, you must give him one.

I assume your question is somehow related to your landlord's entry. Please note that even though a landlord has a key to your apartment, there are legal restrictions on a landlord's right to entry into rental property. You do have legal recourse against a landlord who violates these restrictions.