In his letter firing James B. Comey as FBI director, President Trump included a very pointed reference to the bureau’s investigation into Russian meddling in the 2016 election.

“While I greatly appreciate you informing me, on three separate occasions, that I am not under investigation, I nevertheless concur with the Department of Justice that you are not able to effectively lead the Bureau,” Trump wrote.

That Trump chose to make that point explicitly in what he clearly knew would be a very public letter is no accident. Trump reportedly pressured the director of national intelligence and the head of the National Security Agency to push back publicly on reports about the FBI’s investigation into any links between Russia and his campaign. That investigation was repeatedly disparaged by Trump on Twitter, as well.

On Wednesday afternoon, the Senate Intelligence Committee published Comey’s prepared remarks for his testimony before that body Thursday. From those remarks, we get the first real confirmation that Comey had indeed, on multiple occasions, told Trump that he wasn’t under investigation. But critically, we also learn why Comey didn’t make that public.

In his testimony, Comey describes having told the president-elect during their first meeting at Trump Tower on Jan. 6 that the FBI “did not have an open counter-intelligence case on” Trump. The decision that it was acceptable to convey that to Trump was made in discussion with the FBI’s leadership team, and Comey revealed it without being asked.

Comey then describes a conversation on March 30.

I explained that we had briefed the leadership of Congress on exactly which individuals we were investigating and that we had told those Congressional leaders that we were not personally investigating President Trump. I reminded him I had previously told him that. He repeatedly told me, “We need to get that fact out.” (I did not tell the President that the FBI and the Department of Justice had been reluctant to make public statements that we did not have an open case on President Trump for a number of reasons, most importantly because it would create a duty to correct, should that change.)

We put the critical part there in bold: Comey didn’t want to create “a duty to correct.”

What does that mean? We spoke with Joseph Lewis, who spent 27 years with the bureau before retiring in 2004 as deputy assistant director for the FBI’s organized crime branch.

“Once you make that a story to the public,” Lewis said, “if it turns out that it’s not accurate or not true, then depending on how public you went with it, then you have to go back and try to clean things up.” In other words, if Comey said publicly that Trump was not under investigation, then if Trump were to become a focus of that investigation, Comey would feel an obligation to make that change public as well.

Why do we know it’s worth taking Comey at his word on that? Because it’s precisely what he did to Hillary Clinton last year. After Bill Clinton met with then-attorney general Loretta E. Lynch on an airport tarmac in Arizona, Comey felt the need to speak publicly about the investigation into Hillary Clinton’s email server use as secretary of state. When the FBI later uncovered emails on Anthony Weiner’s laptop, Comey informed Congress — with the side effect of tossing a hand grenade into the presidential race shortly before Election Day. Comey’s “duty to correct” carried the day.

This isn’t a formal policy, mind you. Lewis indicated that the FBI was not now bound by that same duty to correct, if, say, Trump suddenly became a focus of the investigation. It’s a judgment call, he said, but one that would invariably lead Comey personally to sharing that new information, as he did with Clinton. (“That’s just who he is,” Lewis said about Comey, with whom he’d worked.)

Since the FBI investigation was still just gearing up, it was impossible to know whether Trump would be ensnared in it directly.

“You never know where it’s going to lead you,” Lewis said. “That’s why we keep those kind of cases as close to the chest as possible.” Even telling Trump that he wasn’t under investigation was an unusual move, he said. Normally, such information would only be shared when it was imminent that the investigation might become public, such as the issuance of subpoenas.

In other words, Comey wasn’t going to declare publicly that Trump wasn’t under investigation so that he wouldn’t need to then tell the public if Trump was. But the FBI isn’t suddenly bound by that duty to correct simply because of Comey’s testimony. Trump could be under investigation at this very moment — though there’s no evidence that he is.

The irony? At long last, Comey did exactly what Trump wanted: told the world that he wasn’t under investigation as of March. And because he informed the world of that through his testimony, we may never know if that status changes.