Many of the rules are self regulating.
All of the major stock manufacturers know their product has to meet the requirements of the Sanctioning Bodies. All of the major barrel manufacturers produce barrels with contours that are specifically designed to fall within the rules of the Sanctioning Bodies.
It's the same for Custom Actions.
Yes, individuals can alter the product, but this is a very rare occurrence. And besides, if a shooter is serious about spending the time, money, and effort to compete at the top level of the game, the last thing he wants is to throw it all down the tubes with a rules infraction.
So, we come down to weight. This is the one thing that is easy to check. It is also the one thing that is totally controlled by the shooter. And, it is "black or white", so to speak. Either the Rifle's weight is within the rules, or it isn't.
Through the years, the NBRSA has removed quite a few of the rules that had shooters shaking their heads. That ambiguous "1/4 inch depression" thing on bags is gone. "Being able to lift the rifle without disturbing the rest" is gone. The whole "do-nut under the rear bag" got resolved years ago.
So on a sense, Referee's jobs have become more less demanding. The basic one of accepting measurement protest on targets is probably their biggest responsibility, because we don't want individules shooters handling targets during the Aggregate. This is just common sense.
I believe that the rules are in place for a reason. They give us a basic set of guidelines to build by, assuring that there is a level playing field within the classes.
It then comes down to the shooters ability to make the best use of the equipment, and to make the correct decisions when the command of "commence fire" is given.