In view of the intensifying controversy over the politicization of the Department of Justice under Attorney General William Barr and its potential weaponization at the hands of President Trump, it is worth reviving a proposal that has not been seriously discussed since the Watergate era: Congress should transform the Justice Department into an independent agency, legally immunized from the president’s day-to-day control.

The United States government has two kinds of agencies. Most of them are “executive.” They are essentially the president’s agents and subject to his will. This is true for the president’s cabinet, including the Departments of State, Defense, Agriculture, Commerce, Transportation — and Justice.

Other agencies are made “independent” by law. Their heads are appointed by the president, but it is generally agreed that he cannot direct them to do as he wishes or control their day-to-day operations. This is true for the Federal Reserve Board and the Federal Communications Commission. It is also true for the Federal Trade Commission, the Nuclear Regulatory Commission, the Social Security Administration, the Consumer Product Safety Commission and the National Labor Relations Board.

Many people think that under the Constitution, the executive branch is “unitary,” in the sense that the president must be in control of all those who carry out federal law. But since 1935, the Supreme Court has rejected this view, allowing Congress to ensure that these agencies, and many others, operate independently of the president.