Why go overseas to collect the data? Well, there are legal obstacles in the U.S. to collecting phone calls made by U.S. citizens - such a programme would violate the fourth amendment to the U.S. constitution that protects individuals against invasion of privacy. (Exceptions are
granted for communications with foreigners if government agencies suspect terrorism under a 1981 presidential executive order, although they still need approval of the U.S. Attorney General).

But given that U.S. laws stop at the border, foreign spy agencies like GCHQ can legally pick up and store any and all information from data that travels outside the country, suggest reporters at the Guardian newspaper.

"We know the NSA is forbidden from spying on American citizens; in the case of (Faizal) Shahzad (the would-be Times Square bomber in New York), this question remains - was GCHQ doing it for them?" ask the Guardian reporters, noting that the GCHQ now has the "opportunity to build such a
complete record of someone's life through their texts, conversations, emails and search records" allowing it to make a "unique contribution to the NSA in providing insights into some of their highest priority
targets."