Originally Posted by
seawolf
Trusted Traveler is they trust you to not break custom rules and that trust is "earned" based on background checks. It is not trusting your ability to correctly evaluate whether an article is prohibited else they would have required you to take a CBP AG field officer exam during GE interview.

It's a trust that the GE passengers will answer questions honestly in order to facilitate CBP doing its assigned tasks. It is indeed not a trust that the average GE passenger is going to know all the rules for which CBP is tasked.