Is the Justice Department still an independent agency, or are its targets and prosecutions chosen for political gain?

Last week, Attorney General William P. Barr overrode prosecutors’ sentencing recommendations for Roger Stone shortly after President Trump tweeted the sentence was a “miscarriage of justice.” Four prosecutors on the case then withdrew in protest. Barr also assigned a prosecutor to undertake a new review of former national security adviser Michael Flynn’s sentencing, suggesting they are reopening cases prosecuted by special counsel Robert S. Mueller III during his inquiry into the president.

Meanwhile, Trump has been publicly criticizing the Justice Department and FBI for only investigating his allies and not holding his political opponents accountable for their potential misdeeds.

Trump, of course, isn’t the first to push up against the ambiguous status of the Justice Department — which is simultaneously an independent agency aimed at an ideal of impartial justice and an agency that’s constitutionally under the president’s control. All this matters because any whiff of political interference in law enforcement has the potential to undermine fundamental norms of democratic legitimacy.

The Constitution is ambiguous — and that ambiguity benefits the president

One of the reasons the Framers wrote the Constitution was to strengthen the federal government beyond what had existed under the Articles of Confederation. The Articles had included a legislature — but no separate executive branch. As Alexander Hamilton famously stated in Federalist 70, “Energy in the Executive is a leading character in the definition of good government.” One person as president is better, Hamilton argued, than leaving many people to try to make decisions collectively.

Some constitutional scholars have argued the Constitution’s authors intended a unitary executive — an executive branch entirely under the president’s control, with the president free to manage agencies without congressional or judicial interference. Law professors Stephen Calabresi and Christopher Yoo, for instance, have written a number of works arguing this was what the Framers intended, and presidents have behaved this way in practice.

More extreme versions of this point of view argue that executive power is almost unbridled, especially in wartime, since the Constitution explicitly limits congressional power in several places while appearing to leave the president with additional and unspecified executive power. Those who advocate this approach would leave Congress very little say once agencies are created, putting the president entirely in charge of what they do and how they are run. Without going that far, however, the very fact of constitutional ambiguity benefits the president, who can take advantage and act unilaterally, essentially daring Congress or the courts to stop him.

Agencies need to be independent — especially law enforcement

Where does that leave agencies caught between the president and Congress, when each may have differing demands? Most agencies are consistently torn between their two masters — acting on behalf of the president, whom they serve under constitutionally, while remaining responsive to the intentions of Congress, which creates them and funds their operations. Scholarly research finds Congress can control bureaucratic operations (either through oversight or by simply overturning regulations), but there are also significant areas of presidential strength in making important policy decisions.

This tension is particularly acute for law enforcement agencies. During the Watergate scandal, Attorney General John Mitchell misused the Justice Department and the FBI’s resources against President Richard Nixon’s enemies and then helped cover it up on Nixon’s behalf. Since then, those agencies have been expected to be far removed from everyday politics. The Justice Department imposed internal regulations, including ethical guidelines, and a robust Office of Inspector General that can independently investigate any issue helps to preserve this new norm.

However, these are not ironclad protections. The attorney general and director of the FBI are expected to pledge to Congress that they will be independent from the president. Barr himself promised at his confirmation hearings not to allow partisanship or any other personal factors to interfere in his duties. At the time, members of Congress were mostly focused on the Mueller investigation; Barr’s critics suspect the attorney general reported Mueller’s findings in a way slanted to favor Trump. But except among the most rigid adherents to the unitary executive theory, there is widespread agreement that this distance between politics and law enforcement is crucial for maintaining impartial justice and the rule of law.

When law enforcement has appeared even slightly politicized, it has been quickly met with outrage. For instance, in 2016, President Barack Obama’s Attorney General Loretta E. Lynch met on an airport tarmac with former president Bill Clinton at a time when the FBI was investigating Hillary Clinton’s use of a private email server; the meeting was widely condemned at the time. Similarly, George W. Bush’s Attorney General Alberto Gonzales was forced to resign after a highly unusual dismissal of seven U.S. attorneys that reeked of politics.

Democracies need impartial law enforcement

Impartial and fair enforcement of the law is one hallmark of a democratic society. As Steven Levitsky and Daniel Ziblatt demonstrate in their book “How Democracies Die,” leaders or parties that aim at undermining democratic institutions often start by “capturing the referees,” the neutral administrators of the law, such as courts and law enforcement. Once that happens, would-be authoritarians can protect their political allies and punish their opponents.

During the Watergate scandal, Nixon used the resources of the FBI, CIA and IRS against his domestic political opponents. Later, having resigned the presidency, Nixon infamously defended his conduct to journalist David Frost by arguing that “when the president does it, that means it is not illegal.”

Last week, Barr publicly complained that Trump’s tweets were making it “impossible for me to do my job.” Trump responded he had the “legal right” to get involved in law enforcement if he wished. This week, in explaining his pardons of officials who used their offices for personal gain, Trump announced, “I’m actually the chief law enforcement officer of the country.” That echoes his earlier claim that “I have the right to do whatever I want as president.” Nixon’s resignation in disgrace was followed by the election of a Democratic Congress, which enacted reforms. This time around, we will see what voters decide.

William D. Adler is associate professor of political science at Northeastern Illinois University.