Hi, Vicki ...
The rules are that there don't seem to be any rules.
It depends on the ship, the people working and, maybe, the day of the week or the phase of the moon.
In absolute violation of the rules of one cruise line I hopped off the ship in Cozumel (that wasn't the violation part), bought a bottle of rum, walked back ON the ship with the bag and announced, "Don't break the bottle, it's my husband's favorite rum."
How clear is THAT?
They rolled it through the x-ray, handed me the bag, and said, "Have a nice day."
Same cruise, same cruise line, same "rule" I put a bottle of wine in my carryon, just to see what would happen. Nothing. Not at the airport, not at the ship.
I submit that a bottle of wine, once slammed into a hard surface, is a far more dangerous weapon than a corkscrew to open the wine. Flight attendants are now being taught to break wine bottles to use to subdue those who would do bad things.
As a hard-working journalist with high professional standards, I have spent the better part of a year researching this important question on several cruises. So far, I have no good answer and even have photos of the supposedly STRICTEST cruise line boarding people with DFS liquor in one port.
I'm not sure that the cruise lines X-ray anything other than carry-ons. It's the airlines who do the heavy lifting and they couldn't care less if you are toting hooch.
From what I can determine, anything in your non-carry-on bags gets a free trip. What you may have with you in a carry-on or purchase in port OR in the on-board DFS MAY be a different deal, but not always.
My rant on this subject will appear in a well-known cruise travel magazine.
Pamda -- CM First-Time Cruisers Editor and Seasoned Rantess