Yup same procedure in Aus for checked baggage. They cannot open it without you being present. At the airports I have been involved with you can probably count on one hand the number of times that has occurred in a 12 month period.
Thanks Rbwoonton
under the ATSRs, reg 4.18a requires the following sign to be displayed at the screening point:
WARNING!
Screening point in operation
A person at this screening point is taken, by law, to have consented to undergo a screening procedure (except a frisk search), unless the person refuses to undergo the screening procedure. A person who refuses to undergo a screening procedure will not be allowed through the screening point.
So if you wanted to question the screeners authority you would most likely be shown this sign in case you hadn't already seen it.
screeners are working hard to change their public perception. There might be one or two who still have a bit of attitude but overall whether at a major airport or a small regional they are pretty good. That the pax and crews are now well and truly used to the process helps as does the fact that many who go through screening often know the regs better than they do.