Celestia sealed off the area. Nopony would be getting in or out until they were done. Luna… What happened with Luna’s Chironopterae would not happen to any more royal guards. After Luna’s banishment, some blamed her… To a great degree. A conspiracy had taken place, and her life had nearly been ended.
"You will all repeat after me. If you do not, you will be barred from my service, and prevented from coming within casting range of the castle.”
Casting range referred to the distance within which a unicorn could cast spells, a pegasus could drop lightning, or an earth pony could buck or throw something. Upon the invention of devices like the trebuchet, casting range was greatly increased.
"I will swear to uphold the laws and the legislative leaders for the good of all ponydom.
"I will swear to uphold and defend the rights of every sentient being within this realm.
"I will swear to harm nopony, save when another’s life is clearly threatened by them, and never to use excessive force."
Celestia smiled. The updating of the spells by which all royal guards had been updated, and her sister would have someone for whom to come back. Not to mention, if Nightmare Moon’s return was blamed on Luna, she herself would be safe. She realised many centuries later that there would be others to whom her heart would grow close, that her orders would protect.