Addicted to oxycodone

My son is addicted to (shooting up) oxycodone, has to be high all the time! If he can't get pills he has to have spice or pot, lays in bed all day, does not work, asks me for money everyday, now he is starting to threaten me, today he said he felt like assaulting me, if I don't give in to him, he is threatening.

He has been in and out of jail and detox, will not go to rehab on his own, I want him out but he won't go, what can I do?