This is part of the Public Health (Control of Disease) Act 1984, sections 33 and 34: Public Conveyances. An interesting discussion regarding this law (and a few others) can be found here.
Sec. 3-5-20. Alcoholic beverages on public transportation system vehicles. It shall be unlawful for any person to use alcoholic beverages on any vehicle used by any public transportation system operated by Athens-Clarke County. (Ord. of 5-5-92, § 1)
Article III – Parking, Standing, or Stopping Sec. 15 Parking Prohibited: No person shall park a vehicle at any time upon any of the streets or parts of streets described: Main St. (West) In front of Dunkin Donuts to a point 25 feet south. Main St. (East) From the southern entrance of the Municipal office….