Didn’t have to be expanded.
If warrant to tap A leads to recorded conversation wherein B tells A about a crime B has committed, it can be used against B.
But under the FISA rules, B cannot be “known”, unless they are unmasked through 702 requests through the NSA.
FISA gives them great power, but also is supposed to have restrictions.
Did Carter Page discuss a crime with everyone who was unmasked?