A legislação relevante pode muito bem ser 49 Código dos EUA § 46504 - Interferência com membros da tripulação de vôo e atendentes .
An individual on an aircraft in the special aircraft jurisdiction of the United States who, by assaulting or intimidating a flight crew member or flight attendant of the aircraft, interferes with the performance of the duties
A partir do relatório, temos uma testemunha ocular dizendo que o homem ficou muito chateado quando disse que deveria deixar o vôo. Talvez isso tenha sido interpretado como "intimidar um membro da tripulação de voo".
Editar: também o contrato de transporte tem isto a dizer :
UA shall have the right to refuse to transport or shall have the right to remove from the aircraft at any point, any Passenger for the following reasons: ... Whenever refusal or removal of a Passenger may be necessary for the safety of such Passenger or other Passengers or members of the crew including, but not limited to:
Passengers whose conduct is disorderly, offensive, abusive, or violent;
Passengers who fail to comply with or interfere with the duties of the members of the flight crew, federal regulations, or security directives;