Hi XZ:
I've just recently checked into this myself. I've asked my AB to leave on numerous occasions, and he refuses. So, I called the sheriff 's office and asked how to evict him from my home. They said since he's not my husband and I own the house, he's basically a renter. So you need to follow the letter of the law to ensure that your A doesn't turn around and sue you for damages.
So, here's what you need to do (at least in Virginia). You need to send him a certified letter stating that he has 30 days to vacate the premises. If he doesn't leave within that time, then you call the sheriff (or police) and inform them of the situation, show them a copy of the certified letter, and they will escort him out of your home.
The law may be different in California, so check with your local sheriff/police department for specific instructions. Hugs to you. Better days lie ahead.