Actually this has been the Written law in Austin for years....The Austin PD just never exercised it that way.
I got stopped while smoking a joint on a break at work at a restuarnt on 6th St in Austin in 1984...All the cop did was take my stash and told me to "Get back to Cookin some Food"
The law has always read "Four Ounces or less in one bag" as a Misdemeanor/Citation in Travis County....They don't wanna piss off the UT Students!!!