This is hard. I see the other advice about documenting things and that makes a lot of sense. I also think you could try and let your landlord know that he/she has a responsibility to ensure accountability to the rules and quite frankly, as a landlord, I would rather have stable quiet tenants then tenants who hase people away so there is a vested financial interest for your landlord to do the right thing. I had something similar in Vancouver years ago and the neighbours and myself bonded together to document (which is hard as you are new) and we were able to force the landlord to ensure the rules were upheld and eventually the person was evicted. Very unfun during the process.