However:

To ensure traveler's security, transportation security
officers (TSOs) may determine that an item not on the
prohibited items chart is prohibited. In addition, the TSO
may also determine that an item on the permitted chart is
dangerous and therefore may not be brought through the
security checkpoint.

In other words, if they take a fancy to it, they have license to steal it.

-Chuck

Officer discretion based on experience (or accumulated frustration
or bad attitude) teaches them to react autonomously such that
any outcome is possible, ranging from looking the other way to
field execution.