I have been put in a situation like this by my admin, and I will tell you it sucks! Why can't admin do it if they feel it is needed? But then again...it is part of charge nurse duty isn't it...to ensure safe patient care, and that all facility policies are being followed.
Sadly you really must do what they say and report a violation if one is seen. I know it is a horrible situation to put you in, but the nurse is not following facility protocol/rules and must be disiplined (ouch...I know, some rules are silly looking but still must be followed...even on just on a basis of work ethics).
That is very sad, to see that a good nurse can be shot down so easily for not following a rule that does no pt harm or risk safety! I had to fire two awesome nurses because they were in a hurry after lunch and one had to use the bathroom so the other nurse clocked her back in to save time and get back to work...this was cause for dismissal (you can not even touch another persons time card, let alone clock them in/out). I was mad and in tears when I had to let them know, and that they were needed in the admin office...they knew their checks and pink slips were filled out
But bottom line, that was part of my job...and had to do it or my admin would find a way to make me also guilty by not reporting it.