My parent is in assisted living. He can not perform his basic daily needs without assistance. He is a fall risk, almost entirely bound to a wheelchair and can not speak anymore. Yet he is competent mentally. He insists on coming to live with my family. We are against it for many practical and personal reasons which we've explained many times over. Now he is threatening me with legal action saying he can not be forced into assisted living. He was not forced. He signed documents to be admitted. He was reluctant but he knowingly agreed to enter assisted living. They take great care of him but he feels he doesn't belong there. How am I obligated to bring him in with us? I know in my gut that it is the wrong thing to do.
Another thing you (and everyone) should consider. Once you have an impaired person in your care, and especially in your home, it's extremely difficult to find an exit plan. In some states, you can be liable for neglect if you want to stop taking care of him. It's difficult to evict someone who's relying on you for help and care. We've seen several variations on that theme on this very board. Don't even think about it. Tell him he's free to move out of the AL, but he will have to take care of himself or arrange his own care from that point on. I agree with Countrymouse ... call his bluff!
Good heavens, doesn't your Dad realize he is in assisted living because that is the best place for him because of his physical disabilities? Could he be in denial of his condition? Maybe he doesn't really realize that he needs 168 hours of care per week, and if he did move in with you, he would need 3 caregivers per day, and 3 more on the weekends... that is more expensive than him living at his assisted living.