You're still seeing civil contracts and missing the criminal aspect. The ticket is a civil contract. It was violated, and the penalty for violating a civil cont

You're still seeing civil contracts and missing the criminal aspect. The ticket is a civil contract. It was violated, and the penalty for violating a civil contract is generally monetary, i.e. they owe him the price of his ticket, or can be sued for it. The conditions on it are the conditions under which he is not entitled to a refund if he does get kicked off. Criminally, they do have the authority to remove anyone from the aircraft at any time, for any reason or for no reason at all. They can call on law enforcement to enforce that decision, and law enforcement has the right to use the necessary level of force to carry out that decision. They missed several good opportunities to de-escalate the situation have have a PR nightmare on their hands, but their legal liability for anything involved with this is quite low.