Cops will tell you to pull over so they can shine a flash light up your butt just in case you have chopped up leaves or a chemical that only effects you.
Discussion
In my ideal world an adult can walk into a store and buy pharmaceutical grade heroin.
Yeah, I people who want to do drugs are going to do them regardless of if you make them legal or not. I don't see why it should be a crime to put chemicals in yourself of your own free will.
Drug use is not a crime. Locking people up for drug use is a crime.
The typical argument is that addicts commit crimes, but if you steal something or hurt somebody, those things are already crimes and you should pay for them.
To criminalize the potential to cause harm is the same logic that the gun ban lobby is operating on.