From the Princess FAQ:
We kindly request that you do not bring alcoholic beverages (other than wine and/or champagne) onboard for consumption.
Alcoholic beverages sourced from shore-side and brought onboard, no matter where sourced, will be collected at the gangway for safekeeping and will be delivered to the passenger's stateroom on the last day of the cruise.
A member of the ship's security staff will be at the gangway to assist passengers with the storage of their alcoholic beverage purchases. The only exception to the above rule, is that passengers are permitted to bring one bottle of wine and/or champagne per person purchased in a shoreside location onboard. If the wine and/or champagne is brought to the dining room for consumption, a $15.00 per bottle corkage fee will be applied to the passenger's shipboard account. We prefer that passengers bring wine/champagne no larger than 750ml, however, magnums are acceptable. Wine in a box is not encouraged.
Passengers are also permitted to consume the wine and/or champagne in the privacy of their stateroom only, but it may not be brought into any public lounge for consumption.
Please note that any wines and champagnes supplied from the ship's stock to passengers would not be subject to a corkage fee.