On Morning Joe, Hallie Jackson discussed some new details about the Bannon subpoena this morning -- that, and the fact that the White House is making up new rules and calling it "executive privilege."

"So this was a discussion that the White House, I'm told, had been having with the House Intelligence Committee about what exactly Bannon might or might not be able to say and apparently instructed Bannon to avoid certain questions related to his time at the White House. That's one of the subpoenas, the congressional subpoena," Jackson said.

"There's also the grand jury subpoena from the special counsel, arguably and potentially more impactful here. We have new reporting on how exactly all of this went down. A source familiar with the proceedings says FBI agents actually showed up to Bannon's house last tuesday intending to talk to him, serve him with the subpoena, unaware that he had just retained counsel -- William Burke, who represents two other people related to all of this, White House counsel Don McGahn and former White House chief of staff Reince Priebus.

"Bannon said I have a lawyer, you've got to go through him. The subpoena was served to Burke. The subpoena does compel Bannon, as Michael Schmidt broke and reported and we'll talk about, it compels him to speak before a grand jury. But Bob Mueller could still give Bannon potentially an option, to voluntarily interview just like we've seen so many other people connected to this Trump administration do.

"I'm told by a source close to Bannon that if that option is offered, Bannon will take that and do this interview, and the timing of that is very soon, likely some time before the end of the month. The question of course is, why did Bannon get the subpoena? So far as we know, Bannon is the only person actually served a subpoena by the grand jury. What is that about? Three people with knowledge of the case have raised the possibility that perhaps it is because Mueller is in essence attempting to thwart any possibility of potential intimidation, for example, or pressure by the White House to get Bannon not to comply or not to answer, certain people's view that this could be the reason for this.

"Although it's still not clear. So there's a lot of sort of back and forth as to how this went down. the bottom line is, Bannon is going to have to talk with Bob Mueller's staff, Bob Mueller himself one way or the other -- in front of the grand jury or voluntarily in an interview."