I think this might fall under the U.S. Customs service as a “gift.”
http://www.customs.treas.gov/top/contact.htm
You must state on the Customs declaration, in United States currency, what you actually paid for each item. The price must include all taxes. If you did not buy the item yourself—for example, if it is a gift—get an estimate of its fair retail value in the country where you received it.
And here’s the rules for importing alcohol from Greece. Other rules apply from other locales.
Alcoholic Beverages: One liter (33.8 fl. oz.) of alcoholic beverages may be included in your exemption if:
[ul]
[li]You are 21 years old.[/li][li]It is for your own use or as a gift.[/li][li]It does not violate the laws of the state in which you arrive.[/li][/ul]
Federal regulations allow you to bring back more than one liter of alcoholic beverage for personal use, but, as with extra tobacco, you will have to pay duty and Internal Revenue Service tax.
While Federal regulations do not specify a limit on the amount of alcohol you may bring back for personal use, unusual quantities are liable to raise suspicions that you are importing the alcohol for other purposes, such as for resale. Customs officers are authorized by Alcohol Tobacco and Firearms (ATF) make on the spot determinations that an importation is for commercial purposes, and may require you to obtain a permit to import the alcohol before releasing it to you. If you intend to bring back a substantial quantity of alcohol for your personal use, you should contact the Customs port you will be re-entering the country through, and make prior arrangements for entering the alcohol into the U.S. Having said that, you should be aware that……
State laws may limit the amount of alcohol you can bring in without a license. If you arrive in a state that has limitations on the amount of alcohol you may bring in without a license, that state law will be enforced by Customs, even though it may be more restrictive then Federal regulations. We recommend that you check with the state government before you go abroad about their limitations on quantities allowed for personal importation and additional state taxes that might apply.
In brief, for both alcohol and tobacco, the quantities discussed in this booklet as being eligible for duty-free treatment may be included in your $400 (or $600 or $1,200) exemption, just as any other purchase would be. But unlike other kinds of merchandise, amounts beyond those discussed here as being duty-free are taxed, even if you have not exceeded, or even met, your personal exemption. For example, if your exemption is $400 and you bring back three liters of wine and nothing else, two of those liters will be dutiable. Federal law prohibits shipping alcoholic beverages by mail within the United States.
Summarizing, it looks like you can bring back a one liter gift of alcohol from Greece duty-free. If the gift is more than one liter, you’ll need to get a fair market value estimate before leaving Greece. All this assumes you aren’t violating any laws of the state in which you arrive.