19 C.F.R. § 145.54 – Alcoholic beverages.

(a) Nonmailable. Alcoholic beverages are nonmailable, with certain exceptions (see 18 U.S.C. 1716 and the postal regulations), and when imported in the mails are subject to seizure and forfeiture under 18 U.S.C. 545.
(b) Seizure. When alcoholic beverages are received in the mails, they shall be seized, and the addressee shall be advised that they are subject to forfeiture and that he has a right to file a petition for their release (see part 171 of this chapter).
(c) Conditions for release. If the port director is satisfied that there was no fraudulent intent involved, he may release the alcoholic beverages to the addressee upon the following conditions:
1. (1) Applicable duty and internal revenue tax shall be paid.
2. (2) The addressee shall comply with the alcoholic beverage laws of the State to which the shipment is destined.
3. (3) Any other conditions the port director may impose under his authority to remit or mitigate fines, penalties, and forfeitures shall be complied with.
4. (4) The addressee, his representative, or a common carrier shall pick up the merchandise at the Customs office where it is being held. Since the merchandise is nonmailable, it cannot be delivered by the Postal Service.