I just wanted to say one thing.
Mr. Lee's example demonstrates the illogic of it. You're in possession because you didn't use the drug, right? The point is that if the whole point of the section is to stop people from driving while drugged, possession is actually counter-intuitive. You want to charge the person who has the bar receipt in their pocket, not the 24 of beer in their car, because they're not the danger; it's the one who has the receipt for the 24 but doesn't have the 24 any more. So your example makes perfect sense for why it's illogical.
Thank you.