Sgt. Nightingale has clearly, even by his own mitigation plea in the CM,
broken the law (as it is today) and chose to plead guilty to doing so.
The question has been asked many times in connection with this case, "Is it one law for them and another law for the rest?".Given the nature of their work and the nature of their lives either overseas or in Herefordshire I think it is highly likely their interpretation of the civilian rules is very much at variance with your average man in the street and yes, I suspect they may well stick to some of the rules, as they were, a long time ago, I doubt they ever changed in some cases.
(As the near full skip of surrendered weapons would suggest).