Wouldn’t a grant of immunity cover that ?
That’s a hell of a good question, I must admit.
Is it even possible to give a CIA agent immunity (current or former)?
My gut tells me this ends up with the CIA basically telling any Congressional investigative committee to go f*** itself and the proceed to stonewalling. End of story.
There is an alternative....closed-door, off-the-record hearings, with the testimony classified as “National Security” and all those involved forbidden to publicly disclose the results under penalty of law. That’s actually a distinct possibility.
I don’t think immunity is the issue. The CIA would cite “national security” as an excuse for not allowing him to reveal classified information. That excuse would not work in a closed session, but then we the general public would not learn what happened.