It is written in our divorce decree that he has supervised visitation, and that it is supervised by me. However, nothing about his drug addiction has ever been documented.
Start documenting like Beth Suggested. Every time he comes to visit. Then you petition the court to change the Supervision to a Social Worker from CPS as it has become 'emotionally and mentally' challenging dealing with his mood swings, his outbursts, etc. When you petition, with some proof, be it nasty emails, ranting text messages,etc is when you also petition that he has to be drug tested, preferably hair or blood, no UA.
You may need your attorney again, but before you do that, talk to the Clerk of Family Court. Many times the Clerks are very helpful in assisting with what paperwork you need and how to word it.
That way, you have also 'beat' him into court. Also see if the pharmacy(ies) he uses will print you out the prescriptions filled for 2011, "for your taxes." Many will, and you will be able to have a record of how he is 'doctor shopping' and how much he is using and of what.
If his lips are moving you can pretty much accept that he is lying. I would get a nanny cam and a voice activated recorder, so that when he does visit her at your home, you will have it on video and on tape just how he is acting, what he is saying, and how absurd he can be.
J M H O
Love and hugs,