I was talking to my brother about this and he maintains this is the main reason they will not legalize maryJ:
They cant make money off of it!
It goes beyond mere manufacturing and taxation its all the ways the govt and local municipalities can get paid.
Look at it this way the gov/auto makers could virtually eliminate drunk driving if they added a breath-alyzer to all cars. It would work like a kill switch and not allow the car to start till a breath with legal blood alchohol level was blown into device.
The reason they will not add the device is that each DUI brings in at least $10000 in court cost and legal fee's.
Now back to MaryJ they have no QUICK way to determine if a person is high off MaryJ.