“but you are high if you smoke one joint”
And you are drunk if you drink a gallon of whisky too.
So it’s all about the quantity then?
Should half joints be legal?
Yes, you are drunk if you drink a gallon of whiskey.
Drunkenness is a crime, already.
You might argue that one puff of the currently very high THC joints should be legal. I might agree with you in concept. But it would be so ridiculous to enforce - that is unenforceable.
If you were able to smoke 2, 3 joints without being impaired, I’d see the equivalence to 2, 3 drinks.
But you can’t.