Carnival Cruises sail under the Panama flag. So they only have to hold to that country's laws, when outside of the 12 nautical miles away from the coast of a country. So, if none of those rules contradict the laws of Panama, they can do it.
You have a choice in this too. You can refrain from using their cruise service in favor of another one. Besides, Carnival Cruises is considered one of the worst in the business by many people, Royal Caribbean has quite a bit better reputation. A friend of my wife characterizes the difference like riding "Spirit Airlines" (Carnival) versus riding "Delta Airlines" (Royal Caribbean). You don't have to give them your money, if you feel their rules will hinder your enjoyment of the cruise experience.
You have a choice in this too. You can refrain from using their cruise service in favor of another one. Besides, Carnival Cruises is considered one of the worst in the business by many people, Royal Caribbean has quite a bit better reputation. A friend of my wife characterizes the difference like riding "Spirit Airlines" (Carnival) versus riding "Delta Airlines" (Royal Caribbean). You don't have to give them your money, if you feel their rules will hinder your enjoyment of the cruise experience.