I think they should have all three , fine prosecute and banish.Wouldn’t be much different than using a fake passport, fine them and prosecute! Banning them for life might not hurt them in the pocket as much as a hefty fine and criminal prosecution.
Dealing wit thousands of people from all sorts of countries with various histories of "Security" levels will likely mean that this will continue. Not only in the cruise industry. I think Governments will likely leave enforcement up to the Industry at the dock.I feel they should be banned for life. Think of how many that have come on in the past filling out the medical forms saying they were fine then you see all the stories of all the people that got sick on cruise ships.