out standing in our fields

Daniel 4, thanks for your reply. You are certainly correct in noting that the typical Yank tends to believe that his constitutional rights remain the same at all times and places in the US, despite common knowledge of situations where this is not the case, e.g. freedom of speech not extending to causing panic by shouting “Fire!” in a packed movie theater. (Cue the Big Brother icons decrying the imminent annihilation of the First Amendment.) A person’s Fourth Amendment rights are similarly curtailed at US ports of entry on US soil, and are restored once one passes through CBP’s gate.

Please note that the formal name of McCarran-Walter (in my reply above to Chris_Maresca) is the Immigration and Nationality Act of 1952. (There was a large amending act of the same name in 1965.) I’ll point you in turn to §287 (a) of McCarran-Walter for a list of powers that the immigration people can wield without requiring warrants, or even probable cause.