Journalists were reminded again last week of how little legal protection actually exists when the federal government decides to investigate national security leaks.

In an ongoing Freedom of Information Act suit, the Freedom of the Press Foundation has sought the guidelines used by the Justice Department in deciding when federal agents can use National Security Letters to pursue information about reporters. DOJ recently produced documents in response to the suit. They confirm that the rules governing the use of NSLs in media leak cases remain classified. That undue secrecy cripples any real opportunity for public oversight of a process already encased in layers of secrecy.

DOJ’s position is a disappointment but hardly a surprise. In 2013, DOJ found itself in the center of a public storm when it was revealed that federal agents had secretly gathered telephone and email records from reporters at The Associated Press and Fox News during national security leak investigations. The investigators wanted the records to track down the government employees who had passed information to the press.

The AP and Fox revelations led to a series of meetings between Eric Holder and news organizations and ultimately to DOJ’s decision to revise its own guidelines for when subpoenas can be used to obtain reporters’ records. The guidelines were first implemented more than 40 years ago, and they recognize the chilling effect that subpoenas have on reporter-source relationships and therefore on the flow of information to the public. The guidelines are designed to make subpoenas targeting reporters a last resort, issued only after a high-level review within DOJ. Because there is no federal statutory privilege for journalists, and the courts have backed away from finding such a privilege in the First Amendment or common law, the guidelines are in fact an important bulwark against investigative overreaching by federal agents. The revised guidelines, released early in 2015, were intended to strengthen the protection afforded news gathering.

Fairly read, the revised guidelines do that — but even as the revisions were being hammered out in discussions between DOJ and representatives of the press, DOJ made clear that the guidelines would not apply to NSLs. It is a carve-out that cuts deeply.

It is not just that NSLs, typically used to obtain communication records from third parties, have none of the judicial oversight that attends to subpoenas. There is also the damaging impact of secrecy. An important element of the DOJ subpoena guidelines is providing news organizations with notice when their records are sought, subject to some specified exceptions. Notice gives an opportunity not only to make legal objections in court, but also to invite public scrutiny of government overreach. Jim Risen, the target of the long-running subpoena fight in the Jeffrey Sterling Espionage Act case, ultimately lost his legal challenges when federal prosecutors sought the identities of the confidential sources he used in reporting on the CIA’s deeply flawed efforts to undermine Iran’s nuclear capabilities. But there is no question that Risen’s ability to make his case to the public — to remind people of the importance of the confidential sources, of the chilling effect that subpoenas can have, and of his own commitment to go to jail to protect a source — played a role in the prosecutors’ belated decision to drop the subpoena after years of seeking the right to compel his testimony.

That the government has doubled down on secrecy by claiming the right to classify the rules that DOJ uses in deciding when NSLs can be employed to target reporters is made all the more troubling by documents obtained last year by The New York Times and its reporter Charlie Savage in another FOIA case. In a lawsuit that is ongoing in the Southern District of New York, we have sought to have DOJ declassify additional portions of the Inspector General reports on surveillance.

Responding to the suit, DOJ last year released thousands of pages of documents following both a classification and FOIA review. Included in the release was a redacted account from a 2010 DOJ Inspector General report of three leak investigations in which agents secretly obtained records of reporters in violation of DOJ rules (apparently using investigative tools other than NSLs). The three cases involved The Times, the Washington Post, and an unnamed third news entity. In each instance, records were obtained from cell phone providers or other communications companies.

The Inspector General’s language was unsparing: “[T]he FBI’s acquisition of these records constituted a complete breakdown in the required Department procedures.” There were, the Inspector General concluded, “serious lapses in training, supervision, and oversight [that] led to the abuses.” The IG report notes that the law enforcement investigators claimed to be unaware of the special approval requirements that were in place for subpoenaing reporters’ records, and the federal prosecutors said that “they did not correctly understand that the terminology used in the subpoenas or attachments could result in the acquisition of reporters’ records.”

While the takeaway might be that the rules do not matter if agents and prosecutors are going to disregard basic professional obligations, the cases also serve to remind that, for NSLs, internal rules are our only real hope for a check on abuse. And that is why having those rules subjected to public oversight is critical.

DOJ has said that the NSLs are “subject to an extensive oversight regime.” But it is impossible to know whether the kinds of procedures baked into the subpoena guidelines — for instance, a showing by the prosecutor of proven need and a lack of alternative ways of getting the information sought — are mirrored in NSL guidelines. If they are not, there is every incentive for investigators to look to NSLs and avoid the restrictions of the subpoena process. (In my experience, leak investigations overwhelmingly arise from reporting about national security, making them NSL-eligible.) But the classification of the NSL rules takes meaningful discussion of even such a threshold concern off the public agenda.

That level of secrecy is impossible to square with any fair notion of transparency or any realistic assessment of what national security requires. Whatever we may think of the DOJ subpoena guidelines, we at least know what they say, and we can argue about their adequacy and their deficiencies and how well they balance law enforcement needs and the protection of press freedom.

All of which raises an obvious question: Why is it that DOJ cannot provide the same level of transparency when it comes to the NSL guidelines?