Here's some info I found during various searches on this subject. I also remember from a law lecture given during command upgrade that if a passenger changes their mind and no special arrangements are required, ie doors open and on the airbridge/jetty and in the absence of an emergency then you cannot really stop them. The company/airline may however sue for any delays etc. The small print on a ticket may further provide some information on this subject. The ticket being a legal contract. Enough of me here's the article.
Are Air Passengers Entitled to Disembark an Aircraft While Grounded?
Background
After the August 2008 Spanair crash in Madrid, the debate resumed as to whether passengers whose aircraft is stranded on the tarmac have the right to return to the gate once the doors have closed and the aircraft has pushed back. On a separate occasion, passengers recently refused to reboard after they left the aircraft following maintenance work. Pilots and other airline representatives sometimes even face criminal prosecution initiated by passengers for alleged deprivation of liberty pursuant to Section 239 of the Criminal Code. It appears that passengers in such situations feel that they have been locked up against their will. __In this context the question arises as to whether the captain of an aircraft has legitimate powers to deny deboarding and, if so, how the limits of such powers can be determined.
__Legal Situation __
Section 12 of the Aviation Security Act outlines the air carrier's duties and competences. It provides that the air carrier is entitled to maintain law and order onboard its aircraft. The captain is entrusted with public powers which make him or her responsible for safeguarding the passengers’ safety and security. The captain's position is sometimes compared in jurisprudence to that of a police officer exercising sovereign powers. This corresponds with Section 3 of the Air Traffic Order, which empowers the captain to take all measures deemed appropriate to provide for a safe trip. __However, the captain must observe the limits of his or her discretion. He or she may take only those measures that are required and commensurate to avert a dangerous situation. Thus, the pilot must act proportionately when considering the restriction of commensurability. __In many cases the pilot would be ill advised to satisfy a passenger’s wish to leave the aircraft when the aircraft is stranded on the runway. First, the pilot must follow the instructions of air traffic control. Therefore, he or she will seldom be in a position simply to taxi back to the gate. Second, if the passenger is travelling with hold baggage, this luggage must be unloaded. Pursuant to Annex 5.3 of EU Regulation 300/2008, "unaccompanied hold baggage shall not be transported". __Air traffic is international by nature and crossing borders is at the heart of the business. Thus, national regulations and jurisdiction over the aircraft, and the captain’s publicly entrusted powers, would come to a sudden end if there were no conventions under international public law providing for appropriate competences. __Where an unruly passenger is demanding to exit the aircraft, Article 6 of the Tokyo Convention states that:
"The aircraft commander may, when he has reasonable grounds to believe that a person has committed, or is about to commit, on board the aircraft, an offence or act contemplated in Article 1, paragraph 1, impose upon such person reasonable measures including restraint which are necessary:
(a) to protect the safety of the aircraft, or of persons or property therein; or _(b) to maintain good order and discipline on board; or _(c) to enable him to deliver such person to competent authorities or to disembark him in accordance with the provisions of this chapter."
In addition, many airlines lay down such powers in their conditions of carriage and thus provide for a contractual basis to exercise these rights. The airline and the passenger are bound by a contract of carriage under civil law.
__Comment __
An air passenger has no legal grounds or entitlement to request to leave the aircraft once the doors have closed after boarding is completed. The reasoning under German law and additional international agreements is that pilots are best suited to judge the situation at hand and will not put themselves, their crew, passengers and other third parties at risk voluntarily or with levity. __On the contrary, if a passenger decides to force his or her way off the aircraft, he or she may face damages as well as criminal prosecution. __In addition, the practical problems and safety ramifications should not be underestimated. It is simply impossible, from a safety and security perspective, to allow passengers to leave the aircraft on movable staircases on the tarmac, unload their luggage and walk back to the gate across the runway.