Thank you for posting the Link, Karlie, I was just about to. This article has the Princess policy:
This is what we like to see, a comprehensive, no-nonsense policy that tells you exactly where you stand:
Question: What is the alcohol policy onboard Princess Cruises?
Answer: We kindly request that you do not bring alcoholic beverages (other than wine and/or champagne) onboard for consumption. Alcoholic beverages that are purchased duty free from the ship's gift shop or at ports of call will be collected for safekeeping and delivered to your stateroom on the last day of the voyage. A member of our Security Staff will be at the gangway to assist with the storage of your alcoholic beverage purchases.
Question: What are the age restrictions for alcohol consumption and access to the casino and disco?
Answer: The legal drinking age of 21 years is always observed onboard and proof of age may be required. All onboard staff are trained to take seriously their responsibility to not serve alcohol to underage passengers. The age restrictions are clearly posted in the bars. Entry into the disco is limited to passengers 18 years and older. Be sure to check with the child and teen centers, however, for special disco events designed just for kids. Children under the age of 18 are welcome in the gymnasium, spa and Jacuzzi; and also in the evening entertainment show lounges when accompanied by a parent or guardian.
In line with domestic age limits, as well as Princess' company policy, the casino is reserved for passengers 21 years and older. Additionally, only those passengers 21 years and older will be allowed to purchase or consume alcohol. For those whose age is questionable, picture identification may be requested.
It does say you can bring wine aboard, so the original post was a air question, because the policy does not state how much you may bring.
The answer most likely that if you showed up with a case you could show them the above (it is from their own web site) and argue your right. However, I sense that they mean it to be up to two bottles per entrance.
Therefore, the suggestion of buying it in different ports and bringing it onboard is a good one. Also, although they don't state it here, there may be a corkage fee if you want to drink it in the dining room. Most cruise ships that allow wine on board charge one, but not if you drink it in your cabin.