Are you sure about that? Maybe your locale is different, but the DUI/OVI statute in the part of the US where I live is for influence of "alcohol or drugs" specifically. And it absolutely does have a list of what qualifies... and that list basically includes all drugs and alcohol.
Part of the criminal element of DUI is someone's choice to alter their body intentionally. I don't think many would think it would justly apply to natural processes like sleepiness or medical emergencies. That's not to say there shouldn't be penalties for failure to operate a vehicle safely, but those situations are clearly very different than DUI.
What I said there was confusing. I was saying that _I_ was fine with an over-tired person being charged with a DUI as I feel it's just as dangerous and just as elective. It is not the law here. That was unclear, sorry.
The relevant section of the law here is:
(f) It is unlawful for a person who is under the influence of any drug to drive a vehicle.
> And it absolutely does have a list of what qualifies... and that list basically includes all drugs and alcohol.
Does it state that the list is the exhaustive list? I have a hard time believing that someone could be pulled over, obviously inebriated but get off because they were actually on some new synthetic marijuana that wasn't on that list.