When a person goes into treatment for anything from Alcohol, Drugs, Gambling etc-one of the biggest issues is "what about my friends?" You need to have a united front with your family to continue the treatment after leaving the facility-going to meetings, random drug tests, one on one counseling for the addict and the family members. It is very hard because the addict cannot see that the "friend" was actually part of the problem by enabling-whether it be by supplying, or denying to the parent/guardian of the addict. Here is an example that I have seen:
The parent/family of the addict contacts the other parent/family of the friends. Tell them that the child is being treated for the addiction-go into details-pot, OTC meds, etc-give dates and places where child was getting the items. Explain that until further notice, you do not want their child to contact the addict. No email, phone calls, pages, text messages, letters, contact through other friends etc. Explain that under no circumstances will any of those things be allowed to take place. Also, be prepared to get a temporary restraining order. This can and has been done. (Check with the laws in your town/state/provience) . Most parents will have no problem with your requests, but Be ready for the whole "not my kid, my kid would never do that, you are pushing your problems on my child etc". Turn to the support network through the treatment facility/support group-ALANON, AA, etc . There are plenty of other parents that have gone through this and are more than happy to support you in protecting your child. If you have to, as I have seen send a certified letter in the mail to the childs parents, explaining what has gone on if it is too hard to face them. I have seen parents who have taken the friends to funeral homes and asked them to pick out what they wanted their friend to be buried in and if they want matching caskets because that is where their child is headed if they do not get treatment.
Unless that child and their parent/guardian is prepared to go to the meetings and abide by your rules, then they have no business in your childs life. Have a unitied front with your family to protect the child.