The revelation that the U.S. Department of Justice recently subpoenaed a large number of Associated Press telephone records has led to renewed calls for a federal reporter’s shield law.

A shield law generally prohibits compelling reporters to identify their confidential sources and protects reporters’ notes, telephone records and other work product from disclosure. Congress came close to passing such a law a few years ago in the wake of the Valerie Plame/CIA leak investigation, during which New York Times reporter Judith Miller was jailed for contempt after refusing to identify a source. The effort lost steam after the WikiLeaks scandal in 2010, but now, with White House backing, the bill has been reintroduced. But whatever the merits of a shield law, enacting one in response to the AP subpoena would be a feel-good gesture that makes little sense.

The controversy stems from an AP report in 2012 that the CIA had foiled an al-Qaeda plot in Yemen to bomb an airplane bound for the United States. This disclosure apparently compromised an ongoing CIA terrorism investigation. Amid bipartisan congressional demands for action, DOJ launched an investigation to determine who unlawfully leaked classified information to the AP. After exhausting other options, the grand jury subpoenaed the phone records.

Predictably, the tone of most media reaction has been apocalyptic. That no one knows the details of the secret investigation generally has not prevented the confident conclusion that the subpoena was ridiculously broad and abusive. There is wisdom in the old adage, "Never pick a fight with someone who buys ink by the barrel."

A deep breath and a little perspective are in order. The subpoena obtained only lists of phone numbers — no contents of any calls, no reporters’ notes and no emails. No journalists were hauled before the grand jury or threatened with contempt. The records are covered by grand jury secrecy and thus will not be available to anyone outside the criminal investigation or for any other purpose.

Presumably prosecutors want to see whether any phone numbers in the AP records match the numbers of any suspected leakers. With an organization as large as the AP, if you don’t know exactly which phone was used you may have to cast a wide net. As an investigative move, this is a no-brainer. In a case not involving the press, it would be one of the first steps taken. In this case, as required by DOJ guidelines, the phone records were sought only as a last resort, after hundreds of interviews and review of thousands of documents failed to identify the leaker.

LEAK CASES ARE DIFFERENT

Leak investigations are a special breed. The proverbial virtuous whistleblower calls a reporter to disclose misconduct by others — think Watergate, for example. Shielding such a source usually creates no impediment to prosecution, because wrongdoing by others can be investigated directly without going through the source or reporter.

But in a leak investigation the focus is not the information contained in the leak but the act of leaking itself. Disclosing classified information is a crime. It doesn’t stop being a crime simply because the disclosure is to a member of the press. Vague talk about "protecting whistleblowers" obscures the fact that not all sources are virtuous — and some leaks are criminal.

In any leak case there usually will be only two witnesses: the leaker and the reporter. Any suspected leaker has a Fifth Amendment right to remain silent. That makes the reporter the primary — and perhaps only — source of information. That’s why prosecutors consider leak investigations to be almost a no-win proposition. There’s almost no way to succeed without going after information from the press, and if you do, you’ll be pilloried as an enemy of the First Amendment.

That’s also why it’s bizarre to respond to the AP controversy by calling for a shield law. The subpoena came about in the first place due to concerns about protecting national security. But with a shield law, holders of classified information could disclose anything, no matter how damaging, with virtual impunity. They would just have to be sure the recipient qualified as a "journalist" — who is, by the way, the very person most likely to disseminate widely the information meant to be secret.

If we believe safeguarding classified information is important enough to warrant prosecution, why would we also pass a law making that crime almost impossible to prove? Reacting to one subpoena by making future leaks easier would be cutting off our collective nose to spite our face.

Of course, Congress could pass a shield law that would not protect this type of leak. The earlier bill contained exceptions when national security was at stake. But even such a law likely would have made little difference in this case. True, DOJ may have needed a judge to approve the subpoena, but given the nature of the investigation, the exhaustion of other alternatives and the fact that only phone records were sought, prosecutors likely would have gotten most of what they wanted. It’s possible the subpoena would have been narrowed a bit, but that would hardly assuage the AP’s anger. It’s also not clear that advance notice to the AP would have been required.

Leak investigations highlight the tension between our desire to protect classified information and our commitment to a free and robust press. Many believe the government keeps too many secrets. Perhaps the debate we should be having is about reforming the laws that govern how and when information may be classified.

But if we agree there is at least some sensitive government information that must be protected in the interest of national security, and that wrongful disclosure of that information should be investigated and punished, then it makes no sense to undermine those efforts by effectively immunizing leaks to the press.

The arguments for a shield law are weakest when the leak to a reporter is a crime, and there’s little reason to believe a shield law would have prevented the AP subpoena. It would be strange, then, if the controversy surrounding the AP subpoena were what finally led to the passage of a federal shield law — but stranger things have happened in Washington.

Randall D. Eliason is the former chief of the public corruption/ government fraud section at the U.S. Attorney’s Office for the District of Columbia. He teaches white-collar criminal law at George Washington University Law School.