If he had come home to pick up clothes to go to rehab, or to get the number for any number of places that could help him, I might hesitate.
Your son put himself out when he chose to use drugs.
As the mama of a son who also chose drugs, I get through my days by saying a prayer for my son and asking God to do for him what I cannot.
Bringing addiction into your home is not the solution. But maybe if he gets uncomfortable enough, he will seek the solution from the places that offer real help.
I know how much this hurts.
Big hugs from my heart to yours.