DCI 53/97 - but it may have been replaced by now. I cannot quote directly from it here as it is Restricted.
Any move of aircrew back from any location where 'feasible alternatives' such as civil air passage are available (not necessarily 'cheap' civil air) probably contravenes this DCI. Such as flying people back from Incirlik on a trash hauler when plentiful flights are available using civil air passage from Adana?