Originally Posted by
Flaflyer
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.
Firstly, the US government is bound by the Constitution world-wide. Secondly, if it were true that you are "not in the US" at immigration, then obviously CBP would have no authority. If they have authority, then by definition you are on US territory.