http://dataweb.usitc.gov/scripts/tariff/0111c22.pdf

The answer to how much duty will run you if you go over 1 liter is in here, but I couldn't decifer it.... Did note that it depends on the proof and that having to pay Federal Excise tax is also a possibility.

You might also want to look into mailing some back.
http://www.customs.ustreas.gov/travel/travel.htm