The legal answer as to why CPB is allowed to do this is that "reasonable time, place and manner restrictions" can be placed on speech (google that phrase if you want to find cases on it) as long as they are narrowly drawn to serve an important government interest.
Whether this particular one has ever been challenged in court, I doubt it, but I don't doubt that it would pass constitutional muster in a first amendment challenge. An airport is a "nonpublic forum" (e.g., a place not traditionally devoted to speech) which gives the government latitude to impose speech restrictions that are reasonably related to the forum's function. I have little doubt that a court would find that preventing specific criminal activity through the use of cell phones at CPB checkpoints is legitimate.
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.
I would have to disagree. You may not have been admitted yet, but you are certainly on the territorial soil of the US, not on Canada's or Mexico's or wherever you came from. If you started snorting cocaine while waiting in line, and were arrested, you would be protected by the US Constitution, despite your lack of formal admission. Among the many other legal issues that would arise if you weren't in US territory at the time, the LEO's would have no jurisdiction to arrest you. The government can't have it both ways.