Well..I know I will get many arguments here, but the general opinion is that if your BAC is over the state limit you are therefor drunk and deserve a dui.

On the other hand, everyone agrees that you build a tolerance to meds, so taking an amount that may pass one person out, will barely affect a long time user.

I don't see the difference?

Long term alcohol usage is teh same. A moderate drinker can easily register .08 or .10 and not really be impaired.
While an alcohol naive person can register .05 and be stumbling around drunk.