You can bring as much liquor as you want back to the USA but technically only 1 liter per person is Duty Free. You have to declare the rest and it is subject to duty.

Now, for all practical purposes if you are bringing back a "reasonable amount" over the 1 liter Duty Free allowance the Customs agents will usually not assess duty and just "wave you past".

If you are bringing in large amounts (say several cases) you have to obtain an importer's license and comply with the laws governing the importation & transportation laws of the state in which you live.