A person does not commit an offence under Part 3, 4, 10 or 11 of this Act if the conduct which would otherwise constitute the offence takes place—
on board an aircraft, and
at a time when the aircraft is in international airspace.
In this section "international airspace" means airspace other than airspace above Great Britain or above the territorial sea adjacent to Great Britain (within the meaning given by section 1 of the Territorial Sea Act 1987).