You are allowed to enter the USVI or SJU with one liter of alcohol. If you have more there is a duty you may have to pay. If you buy it in the USVI there is a exemption allowing 5 liters.

“You may be asked to show your receipts so it is important to keep a good record of what you buy. This duty-free allowance is double the $800 limit from other islands. You may also take 5 cartons of cigarettes and 5 litres of liquor back as long as one of the bottles is a product made in the Virgin Islands such as Cruzan Rum.”