Does t have to be a FISA warrant. But I’ve seen wiretap, electronic communication warrants. They are like books. Affiant has to show why the information is needed and that, most importantly, there is no other way to access the info.
Between this and what they did to Cohen, it would appear that the FBI/DOJ has rendered attorney-client privilege obsolete.
There was no warrant. The DOJ/FBI is still using the FISA database illegally.
Until the contractors and DOJ/FBI personnel who broke Federal law in accessing this information are prosecuted and jailed, it will not stop.