Prisons (Scotland) Act 1877

32 Legal custody of prisoner

A prisoner shall be deemed to be in legal custody whenever he is being taken to or from, or whenever he is confined in, any prison in which he may be lawfully confined, or whenever he is working outside or is otherwise beyond the walls of any such prison in the custody or under the control of a prison officer belonging to such prison; and any constable or other officer acting under the order of any sheriff, justice of the peace, or magistrate having power to commit a prisoner to prison may convey a prisoner to or from any prison to or from which he may be legally committed or removed, notwithstanding such prison may be beyond the jurisdiction of such constable or officer, in the same manner and with the same incidents as if such prison were within such jurisdiction.