The simple matter here is, Tesla needed to sell cars before the law could accommodate a manufacturer direct sales model. Hence an exemption was carved out, likely at the behest of someone influential, so they could.
Georgia automobile dealerships have way too much power in our state. They were able to shove through without opposition in the legislature a rewrite of taxation on automobile sales. They wanted all used car sales business to themselves and they nearly got it. Now even private party sales of used vehicles are subject to a tax of close to seven percent. Hence, you buy a car from your friend and go to get a tag, you pay that tax based on the assessed value of your car, not what you bought it for. This value is usually lower than trade in value to a dealer, but figure the shock when you buy a 20k car and you need to fork out 1400 for tags.
I am very sure this situation will get fixed quickly. The state wants to appear friendly to tech and manufacturing. Auto dealers, liquor, and cigarettes, are probably the most protected in Georgia but politicians bow to pressure in election cycles to the populace here.
note, the real fear is not Tesla, its that other manufacturers will get to setup stores too.