I'm an ex-drunk who sobered up twenty one years ago. I work with men who are sentenced for DUI in a prison for substance abusers.
The other day I interviewed a young man born in 1992. Eighteen years old, and the judge sentenced him to hard time for a first offense with methamphetamine. This is a nice kid. Most of them are. Our society is upside down.
9 times out of 10 law enforcement is a euphemism for tax collection.
In my (not so) humble opinion, any law based on an arbitrary number is defacto immoral - the focus ought be on safety and smooth flow.
Of course, there isn’t any money to be made with that, so it’ll never happen stateside.