CBP via a bunch of crazy court cases, basically operates outside constitutional constraints. This is also why DHS has been used as private army by POTUS (snatching up people in unmarked vans in Portland for instance) because they can be ordered essentially directly by POTUS and not have to worry about the constitution.
(By the way, in many countries, like in India, if you do/say that to the police you might lose few of your bones and possibly normal functioning of few limbs and organs. Oh the constitution prevents that just fine here as well and quite strongly at that. The thing is constitution isn't an omnipotent and omnipresent just vigilante sentient being that is available to protect everyone everywhere all the time.)