The law does not prevent people from making decisions, or others from doing immoral things, so selling a car to a physically disabled person who cannot drive is legally fine. But if your father is mentally incapacitated (e.g. dementia), then the contract to lease the car may be void for lack of capacity. If you could show, such as through a doctor's testimony, that your father was not mentally compentent when he entered into the lease, you could get a court to void the lease (deal off; car is taken back; father gets money back) by filing a legal action (lawsuit) if the dealer will not voluntarily take back the car.