Couple of points of clarification:
The typical LEO at an airport is there to arrest murderers, rapists, drug dealers and the occasional flyer who gets too bent out shape at TSA checkpoint. Most work for an airport authority or other local jurisdictions. I doubt the if the typical LEO is qualified to screen a carryon short of recognizing the really obvious (e.g. a gun).
Airport LEO's are there to handle security and law enforcement duties at the airport. Some are employed by the airport/port authority, and some are employed as city police officers that have the airport as their beat. Why would the qualification for screening a bag at the airport be any different than that of a bag on the street? When an LEO at the airport is looking through your bag, they are not concerned about your see through bag or your after-shave, they are searching for other things.
The reports I've read of LEO's (including FBI & air marshalls) questioning FT'ers is that they often don't know which end is up. LEO's come in two basic varieties: beat cops (shooters) and gumshoes (brains, detectives). It's the beat cops & shooters (including FAM's) that you're more likely to encounter at an airport. Many (FAM's excluded) might fly no more often than the typical average American and have little familiarity with the life of a road warrior
Referring to beat cops as "shooters" and lacking the brains of a detective is ridiculous. A lot of the older beat cops have served as detective at one time in their career or chose not to pursue that route in their career for a multitude of reasons. As far as being shooters, most carry a gun their entire career without using it. Is the life of a "road warrior" so difficult to figure out? You travel a lot and carry luggage...seems that it is more difficult for the frequent flyers to figure out how to pack their bags..and they are spotted the signs with the instructions on them.
If a LEO beckons you, you're probably in for some wasted hours
More like minutes...unless they have a good reason to keep you.
And finally, assuming you're sitting at the gate and someone decides that you or your bags need to be searched. Who can make that determination and how intrusive (e.g. pat down, documents, computer files) can that search be?
LEO? There are issues of probable cause and articulable suspicion that a crime has been committed.
TSA? More likely to have the authority, but can the scope of the go beyond checking for prohibited items (guns, knives, etc.)?
The authority to have your bag searched in the secure area is derived from the fact that you are in the secure area. Your bags are subject to search at any time and your consent was implied due to your entering the area. All the secure areas are clearly marked. 99.9% of the time you shouldn't be bothered unless there is reason for them to look at your bag. This is like worrying about astroids hitting the Earth...it could and has happened, but the chances of it happening to you are slim.
No, I am not an airport LEO or a TSA sceener, but I used to play a cop on the streets.