I second that: It really depends -

I had a Probation Officer and told him about being able to order scripts on the internet. He kinda looked around (making sure no other PO had heard me) and just said something along the lines that it was "still a doctor" and was ok. Although, I do keep waiting for the question, "Is this doctor local?" - So far, I've not had that yet and it's been many years.

It's still in that grey area of the law I believe, in regards to drug tests.