But there’s another possibility, and in my view, it’s a more likely one. It fits all the facts, just for starters. It’s this: NSA doesn’t need a FISA warrant to target the Russian banks – or any other foreign entity connected with those banks, or doing business in Trump Tower.

In fact, NSA is, as we know, sucking in trons from billions of online transactions worldwide every day. NSA can look at quite a bit in the Russian bank’s email or commercial server communications without getting a warrant. NSA can also review and make available the metadata for the related communications of U.S. persons without a warrant.

There are bases for recording voice communications as well, for which the rules govern what NSA stores and makes available to other agencies on similar principles, although the specific requirements are not the same as for textual communications. If the focus is narrowly on “phone calls,” as alluded to in Trump’s tweets, the analysis here would still apply.

The trove of IT data is stored for five years, out at that now-infamous complex in Utah, and available for retrieval. It’s only if the FBI, DEA, etc. – some entity with a lawful purpose for retrieving the data – wants to look at the message content of data relating to U.S. persons that a FISA warrant is supposed to be obtained.
We’re in a new world now, in which wanting to look at the content of a U.S. person’s communications is more likely to come up after the fact than before the comms occur. We’re in the world of Big Data.

Which means that, in the course of business as it is now done, NSA was certainly busy collecting at least some communications that ran through Trump Tower, throughout 2016.