Since the Justice department was created by congress as was the office of U.S. attorney I would say that does fall in their area. For that matter they could end the justice department and set up a different law enforcement office.
Pardons are clearly a constitutional power of the President - that’s different. Not Congress’ area.
BTW, that George Washington case was resolved without the courts when he gave the documents to the senate.
The Thomas Jefferson case where his vice President was being investigated went to the supreme court and Jefferson lost the privilige argument. “As for Jefferson’s claim that disclosure of the document would imperil public safety, Marshall held that the court, not the president, would be the judge of that. Jefferson complied with Marshall’s order.”
Hardly, it is called separation of powers.
This is another unserious investigation aimed at keeping SCANDAL and REPUBLICAN in the same headline. It’s much like the Libby trial, another witch hunt that will probably go no where. It would be too dangerous for a potential Clinton presidency to lose the right to executive privilege.