What scope does Title I Fisa have as it pertains to other US citizens not explicitly targeted by the warrant?

Question

Suppose that the FBI obtains a Title I FISA warrant on a John Doe. That is they argue successfully before a FISA judge that there is probable cause to believe that John Doe is a foreign agent. This grants the FBI broad powers to surveil John Doe.

To what extent can this authority extend to surveil US citizens who John Doe is believed to have contacted? Presumably if John Doe makes a phone call with another US citizen, that phone call will be recorded under the authority of the relevant FISA statute. But what if John Doe speaks with Jane Doe in a manner that suggests she may offer important insight on John Doe's activities. Can the FBI under the original Title I Fisa warrant surveil Jane Doe to some degree?

This is not simply a legal question, but a question of practice. My understanding is that much of the legal precedent and standard interpretations of FISA law is itself classified, and that therefore this may be a difficult question to answer.

The motivation for the question is probably clear. There was a Title I FISA warrant approved to surveil Carter Page, who had some degree of contact with the Trump campaign. If the "dossier" providing evidence of Page's criminality were taken at face value, this would seem to give the FBI broad interest in the Trump campaign as part of the Carter Page investigation. Is there any reason to believe the FBI would not believe they had the authority to surveil the Trump campaign/transition/administration as a result?

I'm not trying to encourage fanciful speculation, but attempting to understand what is plausible.

Answer 1

So, as I understand it, if you are the subject of a FISA warrant, any person who is a U.S. Person (as opposed to U.S. Citizen, which is much more narrow... all U.S. Citizens are U.S. Persons, but not all U.S. Persons are U.S. Citizens) may be collected as incidental collection, so long as the person not under a warrant is masked.

There are two scenarios at this point: (1)If we say that Bob is a U.S. Person under a FISA warrant and Bob calls Alice, a U.S. Person who is not presently under FISA Warrant. Alice's communications with Bob do not relate to any knowledge of a crime that Bob is under investigation for. The Agency listening to Bob will mask Alice's name (commonly seen as [U.S. Person1] in all evidence publication, with the number incremented according to number of U.S. Persons in the conversation that are not Bob.). The Agency must seek a court order to preserve the recordings of Bob and Alice's communications or destroy the records within 72 hours.

(2) Bob communicates with Alice, a U.S. Person who is not under a FISA warrant. Alice is a previously unknown willing accomplice in Bob's crime and mentions details pertinent to the investigation. The Agency may retain the recordings without a court order in this situation because Alice is providing evidence of a Crime, even if it is not the crime which Bob is being investigated for. However, this does not allow the Agency to start surveillance against Alice. Until they can secure an individual warrant from the FISA courts to survey Alice, they cannot listen into conversations Alice has where Bob is not present.

With respected to the Carter Page FISA Warrant, the authorities could only to the Trump Campaign as it spoke to Page and any information gathered through means not related to Page would not be available to them. If you recall, early in the Trump Presidency, there was some concerns about Obama's former National Security Advisor unmasking Trump Campaign officials during the transition period at the end of 2016. While these officials were not part of the original intelligence seeking operation, they did meet a Foreign Dignitary (The Crown Prince of Saudi Arabia) who, as a foreign leader, was subject to warrant-less surveillance. Initially the team was Masked because the identities were not important to the nature of the surveillance, but Rice felt it was necessary to unmask that it was senior Trump officials and not just ordinary U.S. citizens.