We really don't want the Justice Department investigating Congress

All sorts of information is now spilling out about how former president Donald Trump's Department of Justice sought to investigate leaks related to the Russia investigation. Under Trump, the department subpoenaed the confidential data of journalists and, apparently, the White House counsel. Both of these are chilling, but arguably the worst violation so far is the Justice Department's investigation into members of Congress, including Adam Schiff, who was spearheading the Russia investigation in Congress.

The reason this is so bad: it actively violated the separation of powers, a core constitutional principle.

The Constitution's framers designed a system in which different branches of government would serve as checks on one other. The basic idea was, in James Madison's famous formula, that ambition must be made to check ambition, so that no one branch could consolidate power in itself and thereby undermine the structure of republican government. With the separation of powers, whenever one branch exercises great power, the others have the capacity to oversee it.

The rules that govern disclosure of classified material are based on executive orders issued by the president. They don't apply to members of Congress — because the president has no jurisdiction over them, and they don't work for the president. For the Department of Justice to investigate members of Congress and seek to determine whether they are leaking classified information thus exceeds the authority of the executive branch.

The laws passed by Congress that criminalize disclosure of classified information almost certainly don't apply to members of Congress. They apply to employees and officers of the federal government — that is, workers in the executive branch. This makes sense insofar as Congress effectively delegated the system of classifying secret information to the executive. Congress could in principle have criminalized leaks by its own members. But it hasn't done so, at least not expressly.

As a result, leaks by members of Congress wouldn't constitute a crime. When the executive branch shares classified information with Congress, it has to trust the people's representatives to keep secrets that are truly crucial to maintain national security.

Congress functions as an official, constitutionally recognized source of oversight over the executive branch. Indeed, even more than the judiciary, which can only assure that the executive branch follows the law when someone brings a case to it, the legislature is the primary institution charged under the Constitution with checking and overseeing the executive. You could formulate it into a simple rule: No congressional oversight, no democracy.

The fact that Congress was looking into possible collusion with Russia by Trump as part of its impeachment inquiry makes this danger clear. If the president can launch inquiries into the members of the branch of government charged with overseeing him, he can short-circuit the power of Congress. To put it bluntly, the president and the Department of Justice could break democracy.

A first step in appropriate reform is for the Department of Justice to announce guidelines according to which it will not investigate members of Congress or subpoena their records unless they are being investigated for a statutory crime such as corruption. Attorney General Merrick Garland said Monday that his department would do so. This would match the Justice Department's recent announcement that it will stop issuing subpoenas against members of the press in leak investigations, a practice previously used by administrations of both parties.

If these guidelines aren't enough to constrain the executive, it might be worth going further, and requiring special vetting by independently appointed, nonpartisan prosecutors before any such investigation could be launched. The closest analogue would be the practice of appointing special counsel to investigate members of the executive branch such as the president.

In our radically polarized political world, the Department of Justice is a formidable tool with the power to subvert democracy. Ideally, the department would be sufficiently independent from presidential political influence that we wouldn't have to worry about the president using it to satisfy his own personal vendettas. But as we knew at the time, and know even more now, the Trump Department of Justice repeatedly violated traditional norms of departmental independence. Now we need formal steps to help restore that independence — fast.