(1) A police officer may, for the purposes of stopping and searching persons or vehicles under this Division or preventing persons entering or leaving an area without the permission of a police officer--(a) place a cordon around a target area or any part of it, or(b) establish a roadblock on a target road (including any road in a target area).
(2) A police officer must not refuse permission for a person to leave the area unless it is reasonably necessary to do so to avoid a risk to public safety or to the person's own safety.
(3) A cordon or roadblock may consist of any appropriate form of physical barrier or obstruction preventing or limiting the passage of vehicles or persons.