No cruise line, that I know of, will allow you to bring alcohol on board with you. Some will allow one bottle of wine per person. Some cruise lines have stopped allowing even water to be brought on board. Sorry, CamperMom, still the same old answer, no scotch from Barcelona
To the point of the OP since this is a Carnival thread, Carnival does not allow personal hard liquor. You can order it delivered to your cabin by calling guest services prior to your cruise but you are paying a premium for the luxury of having a bottle in your cabin.
Disney does allow it but it must be able to be contained in a standard size carry-on bag, so by dimensions they do limit the amount.