Royal Caribbean changed their policy about 2 years ago. You use to be able to bring one bottle of wine or champagne per adult onboard. However, now you cannot bring any alcohol onboard at all.
Here's their official policy (note that liquor is further define as any alcoholic beverage not just hard liquor).
Q: Can I bring liquor or non-alcoholic beverages (from home or from a port) onboard?
A: Guests are not allowed to bring alcoholic or non-alcoholic beverages onboard for consumption or any other use. Alcoholic beverages that are purchased in ports-of-call or from Shops On Board will be stored by the ship and delivered to your stateroom on the last day of the sailing. Alcoholic beverages seized on embarkation day will not be returned.
Security may inspect containers (water bottles, soda bottles, mouthwash, luggage etc.) and will dispose of containers holding alcohol. Guests who violate any alcohol policies, (over consume, provide alcohol to people under age 21, demonstrate irresponsible behavior, or attempt to conceal alcoholic items at security and or luggage check points or any other time), may be disembarked or not allowed to board, at their own expense,
in accordance with our Guest Conduct Policy
. Guests who are under the permitted drinking age will not have alcohol returned to them.