It is surely cold comfort to Hillary Clinton and her supporters that the inspector general of the Department of Justice will conduct an investigation of James Comey’s behavior on the eve of the Presidential election. But the decision by Michael Horowitz, the I.G., to examine the propriety of the F.B.I. director’s disclosure of politically damaging information about Clinton last October 28th was the right one.

The investigation will now raise its own questions—starting with whether it will ever be completed. Horowitz, like all inspectors general, is a political appointee, and these appointees almost invariably leave office along with the President who named them. I.G.s are an exception to this rule—sort of. In 1981, President Reagan fired virtually all the inspectors general because he thought he should have the right to name replacements. This caused a now forgotten political firestorm, and Reagan ultimately backed down and rehired most of them.

In the wake of that controversy, a tradition evolved of allowing inspectors general to serve from one Presidential term to the next. But it’s only a tradition, not a law. The inspector-general law says that I.G.s should be appointed without regard to political affiliation, but it also says that they can be removed by the President. The law also allows the Attorney General to shut down individual investigations. For his part, Comey welcomed the investigation and vowed to coöperate with it. Neither Jeff Sessions, the Attorney General-designate, nor the Trump transition team has so far offered any comment.

It is well within the realm of possibility that the Trump Administration will kill this investigation before it even begins. The President-elect clearly believes that all the recent attention paid to the hacking of the Clinton campaign’s e-mails, apparently by Russian forces, was contrived to deprive him of the legitimacy he so craves. It’s easy to imagine that he will view the investigation of Comey the same way, since so many people have attributed Trump’s election to that last-minute development, rather than to his campaign. The only thing standing in the way of his firing the inspector general is a political norm, and Trump has shown gleeful disdain for such standards. In a similar vein, Sessions (or his deputy) could decide to prohibit the inspector general from conducting this inquiry.

The need for an independent investigation of Comey’s behavior is manifest. By injecting himself into the campaign at the last minute, he violated long-standing traditions and rules of the Justice Department. His revelations were followed by a torrent of leaks from his agency, all apparently aimed at damaging Clinton’s campaign. Inspectors general have no power to fire or prosecute; they may only refer their findings to the authorities with such powers. But these investigators do have a tradition of independence, and Horowitz’s judgment will have important historical resonance—if he’s allowed to make it.