This incident will make things a whole lot more interesting in the future. Let's imagine an unstable, belligerent passenger who the crew believe is a threat to the safety, conduct or good order of the flight that is about to take place. Unless the law is clarified, you might not get help in the future from local law enforcement officers. Now what? Given a weak crew an entire aircraft and those on the ground might will end up paying the price for an altercation at 30,000'. The contractual issue must be separated from the legal issue. This means that if I say to Passenger X "you are not flying" then Passenger X gets offf. By all means make a legal claim against my company for my descison, but there never be democracy or mob rule on an aircraft, if for no other reason than there are only two sets of controls.