My AH gave me his Power of Attorney after the first relapse .........this document only enables you to do business transactions, consent for treatment for children, that type of thing.
You may want to check what the rules are in your state.........but as far as I know the person has to be willing to enter treatment. You can only have a person sent against their will if they are a immediate danger to themself or others ( in my state)
So I'm not sure that a POA will help .