My son rented a place and was remodeling it for the landlord ( with landlord agreement) with a few days he had his now exgirlfriend over with their two small children and they moved in while my son was at work she has since called the law on my son for dimastic violance, and moved a new boyfriend in since she did not have permission to move in and the landlord wants her out immediately what can he do?

Now that they have moved in, and set up residence, even if illegal, the laws to evict must be followed.

I suppose your son could try to have them evicted, but more than likely, the landlord will have to file and evict them, chances are, he may just evict everyone, including your son.

Does your son have a lease? What is the dispositiuon of the domestic violence charge?

Yes the landlord has to formally evict them and he most likely will evict your son as well.