hi and welcome-
i did a bit of research on your question as to whether he has the right to return to the apartment. it appears the laws vary from state to state, so you will have to contact an attorney to determine the law for california. it might be in your best interest to change apartments, i would ask the lawyer that question too.
apparently in some states, it appears that he can indeed return and has legal rights to stay:
"Unless there is a court order for protection, he has a legal right to live in the house. since he is not on the lease, you have to go to court and petition to have him evicted. you have to show just cause as to why he should be evicted, and during this time, legally he doesn't have to pay any bills or maintenance cost in the house. also, it could take up to 90 days. there is also a fee you have to pay the county for the eviction notice, and if the county sheriff has to actually remove the property from the house, you have to pay a "peace bondsman" to guard any property left outside for at least 24 hours. you can't just call the police and tell them to kick somebody out, these laws were put in place to protect "Women" from being evicted by there boyfriends or husbands. "