The screening officers get the authority for their role from:
AVIATION TRANSPORT SECURITY ACT 2004
SECT 97 is interesting.
In exercising a power under this Division, a screening officer must not use more force, or subject a person to greater indignity, than is necessary and reasonable.
Did the research after being yelled at by a "lovely lady Screening Officer" after requesting an explation as to why I had to remove remove my watch when it had not caused issue at 2 other airport screening zones that same day (nor for the several years before actually).
Whilst I understand how difficult their job may sometimes be, and really the majority are pleasant enough to deal with, some unfortunatly need to look at the Act that gives them their authority.
I suggest that if you consider the screening officer has acted outside the above regulation, ask for the supervisor and lodge a complaint.
I know I will in future.
Really the screening industry does not need similar people to the lovely one I encountered.