I`ve not heard of charges laid in respect of the Carnival Legend incident. The ship entered the fishing port of Eden on the south coast of NSW to put off some 8 persons,they were joined by the rest of a large family party. Reports say the family group had been "picking fights" for days. I imagine patience wore thin.
There was another incident just prior on a P&O ship, which returned to Sydney Harbour to offload onto a Police boat a group of men on a "Buck`s Party", and a lady who I read "glassed"(smashing a glass or bottle into the head or face) one of them and was arrested and charged. Tough cruise, it returned early again to unload an injured passenger, possibly in a fall.
Carnival and P&O are lower priced cruise lines which may offer large groups a discount. We did a short cruise on Carnival Spirit(said to be a better experience than Legend), because of timing to celebrate a birthday, finding some passengers quite different to those we met on Holland America, Norwegian,and Royal Caribbean.