I hereby officially proclaim and declare that I am waiving the share of the spice revenue of Arrakis due to me as Sublime Padishah Emperor of the Known Universe! This right is every bit as real as Trump and Bannon's claim of executive privilege.
Why don't they get to claim executive privilege to prevent Bannon from testifying before the January 6 Committee? Two reasons:
executive privilege, to the extent it exists at all, is a power of the office of the presidency. Trump is no longer president.
Even if he were still president, executive privilege doesn't allow the president to restrict the testimony of private citizens.
If Joe Biden calls me up to discuss something (which he should do more often!), he can't then use executive privilege to keep me from telling Congress about it. Bannon was a private citizen throughout 2020-21.
If you don't agree - well then I'll have to take my imperial spice revenue back!