Does he really have to have a warrant?
50 USC 1802 (a) (1) says the President , through the Attorney General may authorize electronic surveillance without a court order to acquire foreign intelligence information for periods up to a year......
It has criteria involved but we know Barky wouldn’t have followed it anyway.
So, did Lynch and Obama do this without a FISA warrant?
We know they applied for a FISA warrant initially and were denied. Then they applied again in October and the warrant was granted. We do not know what was done between those two events. Obama could have invoked the special needs clause and proceeded without the warrant though his surrogates have claimed he didn’t initiate the initial FISA warrant request. We also need to remember that the Bush’s are known to have extensive ties inside the intelligence community and this kind of thing is right up their alley.