4. — (1) A member of the Garda Síochána who has reason to believe that a person has committed an offence under this Act may arrest him without warrant.

(2) A member of the Garda Síochána who has reason to believe that a person who is about to board an aircraft in the State or is on board such an aircraft intends to commit, on or in relation to that aircraft, an offence under this Act may—

(a) prevent the person from boarding the aircraft or travelling on board the aircraft,

(b) without warrant enter the aircraft and remove the person from it,

(c) without warrant arrest the person.

(3) A person arrested under subsection (1) or (2) of this section may be detained in custody for a period not exceeding 48 hours and shall then be released unless before the expiration of that period either he is charged with an offence under this Act or he is brought before a justice of the District Court pursuant to the provisions of section 27 (6) of the Act of 1965 or before such a justice or a peace commissioner pursuant to the provisions of section 49 (3) or 49 (4) of that Act.

(4) (a) Where the commander or other person in charge of an aircraft which is in the State has reason to believe that a person has committed or is about to commit an offence under this Act, he may prevent the person from boarding the aircraft or, if the person is on board the aircraft, he may remove him from it.

(b) The commander or other person in charge of an aircraft shall, as soon as may be after he has, under paragraph (a) of this subsection, prevented a person from boarding an aircraft or removed him from it, notify the appropriate authority in charge of the airport both that he has prevented the person from so boarding or has so removed him and of the reasons for the prevention or removal, and the authority shall, as soon as may be after receipt of such notification, inform the Garda Síochána of such notification.

(5) If a person, who under this section is prevented from boarding or travelling on board an aircraft or is removed from an aircraft or is arrested, is not an Irish citizen or habitually resident in the State, he shall, if he is an alien who, under the law relating to aliens, could have been refused leave to land in the State, be deemed for the purposes of that law to be an alien who has been refused that leave.

(6) Where a person who is an alien who, under the law relating to aliens, could be refused leave to land in the State is in the State by reason solely of having been, under subsection (2) or (4) of this section, prevented from boarding or travelling on board an aircraft or removed from an aircraft or, under subsection (1) or (2) of this section, arrested, the person shall, for the purposes of the law relating to aliens, be deemed not to have landed in the State.

(7) A commander of an aircraft who, or an appropriate authority which, fails to comply with subsection (4) (b) of this section shall be guilty of an offence F2[…].

(8) The commander of an aircraft, a member of the crew of an aircraft, a passenger on an aircraft, the owner or operator of an aircraft or any person on whose behalf a flight was performed shall not be liable in the State—

(a) to conviction in any criminal prosecution, or

(b) in damages in any civil action,

brought in respect of any action taken against any person pursuant to a provision of this Act.