By law, the president and his subordinates must keep the congressional intelligence committees “fully and currently informed” of intelligence matters. This is a standard that has been given more specific meaning by an evolving process of accommodation between the committees and the Intelligence Community. But both branches have tended to reserve their rights, and the executive branch in several internal opinions and briefs filed in the Supreme Court has repeatedly taken the position that the president ultimately controls the flow of classified information to Congress. This position is rooted in separation of powers doctrine, a cornerstone of the American constitution.

Oversight is absolutely essential, but to function properly it must operate honestly, and in reasonably good faith. The House Intelligence Committee, under the leadership of Chairman Devin Nunes, has fallen far short of that mark, particularly in its treatment of the FISA surveillance of Carter Page, as I’ve written, where “it tried to deceive the American people in precisely the same way that it falsely accused the FBI of deceiving the FISA Court.”

The executive branch has also protected the rule of law in part by limiting disclosures to Congress about open investigations. The reasons for this are simple and powerful, as the Department of Justice has previously explained. First, “Congressional inquiries during the pendency of a matter pose an inherent threat to the integrity of the Department’s law enforcement and litigation functions.” In other words, Congress is inherently political, and congressional oversight of ongoing investigations risks enabling political influence—members pressuring investigators and prosecutors to go after this particular Democrat, or this particular Republican.

Second, Congress leaks: “In addition to the problem of Congressional pressure and the appearance of such pressure, disclosure of documents from our open files could also provide a ‘road map’ of the Department’s ongoing investigations,” and Congress could release them to the targets of an investigation either “through inadvertence or a deliberate act.” At present, DOJ and the FBI believe, the New York Times has reported, that “some lawmakers [are] using their oversight authority to gain intelligence about [the Mueller] investigation so that it could be shared with the White House.”

The searing experience of Watergate also gave rise to limitations within the executive branch itself. Since Nixon, every president, from Carter to Trump, has adopted policies limiting interactions between the White House and the Justice Department to protect the independence of prosecutorial decisions. The president may set law-enforcement priorities and policies—but regardless of who is president, a bank robbery is still a bank robbery, and the American people have a reasonable expectation that crimes will be investigated and prosecuted in keeping with the president’s constitutional obligation to “take Care that the Laws be faithfully executed.” The Federalist Papers’ famous warning about the dangers of factionalism, which also recognized that “enlightened statesmen will not always be at the helm,” expressed the principle that “no man is allowed to be a judge in his own cause; because his interest would certainly bias his judgment, and, not improbably, corrupt his integrity.” And the same is true, of course, of prosecutors: We do not trust anyone to investigate herself.