Originally Posted by
garykung
No.
CBP has 2 responsibilities - immigration and customs. So even CBP is not checking immigration status, CBP can still exercise its customs responsibility when it is appropriate. In fact, there are permanent domestic checkpoints within the U.S. serving that purpose, which are all within the U.S. territories due to the fact that these territories have its own customs zone.
But what is their customs responsibility on a domestic flight, particularly in regard to something like financial instruments? To my knowledge, if I'm foolish enough to carry 20k in large bills in my pocket, I'm perfectly within my right to do so, unless I cross a border.