Legal Question in Criminal Law in California

Re: Personal residential privacy and security

If your stepson is an adult then the law treats him as it does any other third party who wants to enter your home. If he is not on the deed or lease, if has no contractual right (with you or another resident) to enter and if neither you nnor any other resident have promised him such a right, then you are as free to exclude him as you are anyone else.

You can only use as much force to keep him out of the house as is reasonably necessary under the circumstances.

Re: Personal residential privacy and security

You can have him arrested for trespass. You can obtain a restraining order against him. You can file a forcible entry and detainer action against him. You could also use the "limits of legal force". The limits of legal force are reasonable force necessary to protect your property and person. It is up to a jury to decide what exactly "reasonable force" means in each situation. I suppose, if you really want to know the limits, you could find out by trial and error. If you end up in jail, well then you know you went too far. If you do not end up in jail, well then maybe you could have went a little bit farther. Or you could try one of the above less risky means.