Get out your popcorn out for this one, which will end up with many matters to be decided by the judiciary.
Jim Jordan will be investigating the Jan 6th investigation – of which he is almost certainly a target. Should an FBI officer be forced to reveal details of an investigation to the guy he’s investigating? The common sense answer is obvious, but the legal answer is not.
Furthermore, there could be a battle of subpoenas. Jordan could be issuing subpoenas to the investigators while they are issuing subpoenas to him to testify about his actions on and leading up to January 6th. The DoJ will obviously challenge any congressional subpoena in court if the subpoena interferes with a criminal investigation, and the Supreme Court will probably have to sort it out eventually. The congressman, on the other hand, can’t ignore a grand jury subpoena. Judges take those very seriously. In the most extreme example, it could actually end up with Jordan questioning a guy one day, then getting arrested by the same guy the next day!