And it is because of those virtues that defending Rosenstein is now a critical imperative for everyone who is concerned about the Trump administration’s erosions of the independence of law enforcement. His removal, if the president can effectuate it with impunity, would shatter long-standing expectations of what federal law enforcement is, what it isn’t, and how presidents can and cannot properly use it.

Trump is livid because Rosenstein has supervised two separate investigations that involve both Trump himself and those close to him, now including Trump’s personal lawyer Michael Cohen—and because Rosenstein has not loosed the Justice Department and the FBI on Hillary Clinton and other political foes of the president. In other words, the president wants to fire Rosenstein because apolitical law enforcement is stronger with him than without him, and the president is at war with the very notion of apolitical law enforcement.

You don’t need to take my word on this point. Trump himself says it all the time—and loudly. He announces at every turn that he thinks the attorney general’s job is to protect him from the Russia probe and that he wants law enforcement to focus on Clinton. Rosenstein is only on Trump’s radar screen at all because the investigation of potential ties between associates of the Trump campaign and Russia required the attorney general’s recusal, a matter about which Trump also serially complains. The president’s attitude toward federal law enforcement is not just corrupt. It is openly and flamboyantly corrupt. He wants the FBI and the Justice Department to be at his beck and call. He wants them to be expressions of his power and interests.

That is a notion of federal law enforcement that this country turned decisively away from over a long period of time. The notion of law enforcement as professional, not political, began developing as an aspiration and an ethos even while in practice the FBI was the personal fiefdom of J. Edgar Hoover. The modern norms of apolitical conduct and independence on investigative matters, which crystallized in the reforms that followed Watergate and the civil-rights era abuses, reflect not merely the shock of those abuses but decades of learned experience about law enforcement professionalism and how to do investigations well under a rule of law system. The question Trump is posing is whether we want to go back to a more primitive vision of the relationship between the president and the civilians with the power to lock people up.

In the face of these expectations on the part of Trump, Rosenstein—after his catastrophic participation in the Comey firing—first began to assert his independence when he appointed Robert Mueller as special counsel. In the months since then, he has assiduously protected Mueller both from Trump and from congressional pressures. He has courted the enmity of the Trumpist wing of the congressional Republican delegation by making clear, repeatedly, that Mueller is not a rogue actor but is instead working under his supervision and keeping him informed. Back in December, he testified that “I know what (Mueller is) doing. I’m appropriately exercising my oversight responsibilities. So I can assure you that the special counsel is conducting himself consistently with our understanding about the scope of his investigation.” He has made clear that he will not remove Mueller absent good cause to do so and that he has seen no evidence of good cause.