This arguement is easily solved in 2 questions
1. Does the thought on Ganja versus MMA PED rule have to be reviewed or revised?
2. If it is a known rule right now (albeit almost as stupid as the no 12 to 3 elbow rule) does that mean people can ignore it?
I would suggest that fighting gifts aside Pat Healy made a idiotic choice in using a. Drug he knows people have been suspended for using in the past. He also knew he had a good chance of being tested for it. He also freely admits that it was for social reasons and nothing more.
If it was clear in his contract, then there is no one to blame but himself.