California  |  Real Estate Law

My property manager, throughout the course of lease, repeatedly dropped by without notices and bullied us, threatened us with eviction, and entered our property without 24-hour-notice or our consent. I am interested in pursuing legal action against them, but I am not sure what law to cite as reason. I have been told that this is totally illegal and a violation of my tenant's rights in California, but I'm having trouble finding the actual legal clause that states this. What should I look at to help form a case? I had 5 roommates who all experienced this treatment.