The lemon laws vary from state to state. But if the Acadia has been in the dealer for the same issue three times within the first 12,000 miles It's time to call it a lemon But....
As far as taking legal action against GM, the laws concerning defective products are limited to many factors one is by mileage and the overall condition of the vehicle.
Just because it's two months old does not mean it has not being abused by improper driving, towing (if any) or unauthorized modifications.
GM Goodwrench technicians have the ability to tell when a vehicle as being excessively abuse with their data analyzer and Tech2 computer connected to the vehicle's ECU.
The ECU is like a black box, it records everything. That's probably the main reason why GM is giving you the run around, the Acadia has being abused and they are NOT taking responsability for your own actions which is totally fair and any judge in the land will say the same thing.