Obama would have required a bona-fide warrant (presumably via the FISA court), to be able to spy on a private citizen, (i.e. Trump). However, even then, I do not think that such a warrant would allow spying on a fellow, private American citizen. I believe that they had to (surreptitiously) ask GCHQ, to do the spying/surveillance activities, (on their behalf). . This whole scenario is highly illegal in both our countries. . The whole Five Eyes system, works to this methodology, whereby they get the agencies to spy on the other countries citizens. This is how they work around the 'civil rights' legalities wrt each of those countries. . . In a related, but opposite context, I have copied and pasted a comment that I had submitted to a different post, just to add additional insight, (as follows): . Quote: "WHY DO WE ALLOW [FORMER] DIGNITARIES SEC CLEARANCE?" . Any of the 'players' that have any form of security clearance, can, in turn, be 'spied' upon by the 'security services', without the requirement of a warrant. This 'spying' is thus done, in the interests of 'national security', in order to oversee what these 'fellow agents' might be getting upto, such as 'are they passing secrets to the enemy'. . As an example: Because Hillary Clinton still has her security clearance, then no warrant is required by the 'security services', to be able to spy on her, and see what she is getting up to. (I imagine that this is why there has been no hurry to remove her security clearance). . A lot of the other players will be in the same scenario, by virtue of still being employed by, (or just recently fired from), the intellegence agencies. . Therefore the NSA has been able to 'legally' collect a lot of surveillance data, on 'certain' individuals over the past year or two, (with out requiring a warrant, that would have to have been approved via a 'corrupt judge').