Originally Posted by
Wiirachay
I The legitimate reason why I think cell phones in customs / immigration is prohibited is to prevent communication between passengers who may be conspiring to bring in illegal materials or entering the country illegally. People can scout out which immigration officers or customs officers are lax or clueless and conspire.
bolding mine. This is the real reason. A scout can go in front of the line and direct the mule lagging behind last off the plane to a lax line. The scout cannot wait till after customs and TSA, as by then Lane 5 might have a shift change and the toughest agent has replaced the lax agent. The phone ban is to prevent real time information sharing.
As for "constitutional rights", it is my understanding that the US Constitution does not apply in other countries. Until CBP is done with you, that is you have cleared both immigration and customs, you are not IN the US. You are still in the country you came from or you are in an international no mans land.
Note that if your passport is no good the term is "refused entry" to the US and they put you back on the next plane back to where you came from, or for those of you walking or driving, they turn you away and you stay in Canada or Mexico. Refused entry means you never entered the US proper. Even though the customs area is in the basement of a landside US airport, you are not in the US till cleared. At least that is how I understand it. YMMV.