if you read the fine print Princess will let you bring a bottle of wine and then charge you a $25 corking fee. They will sell you liquor bottles on the ship but not give them to you until you get off the ship.
So what I do is put my liquor in emtype coke bottles (plastic) and then into a ziploc bag and into my suitcase! When you are in port you can buy bottles of liquor and just put them in a shopping bag and bring them back on the ship. They have never taken it from me. I also buy boxes of wine in ports if I can find something desireable. The other option is to buy the $50 COKE card with unlimited fountain drinks and put your own liquor into the soda. Two people can easily share one coke card if you need the carbination for your desired drink. I keep telling them to make my favorite of crystal light blended in the bar blender with water and ice and then I add my own booze to it= cost me nothing