Forget the "U.S. Code".
THESE are the rules from Royal Caribbean's own website:
Guests are responsible for the behavior or damage caused by their service dog. A cleaning fee may be charged to the guest's shipboard account. If the service dog's behavior creates a fundamental alteration or a direct threat to safety, the dog may be denied boarding or removed from the ship along with the owner at the guest's expense. Examples include: growling, barking excessively, initiating unsolicited contact, biting other guests and/or crewmembers, failure to use designated relief areas, sitting on furniture, eating from the table, etc.