Bipartisan DOJ explanation of AP investigation

No apoligies made for the length.  National security is not amenable to sound bite format.  

The Op-Ed sources:  William P. Barr was the United States attorney general from 1991 to 1993. James S. Gorelick was deputy attorney general from 1994 to 1997. Kenneth L. Wainstein was assistant attorney general for national security from 2006 to 2008.

Why investigation was warranted (direct quotes from the linked article; emphasis mine) 

1. The leak — which resulted in a May 2012 article by The A.P. about the disruption of a Yemen-based terrorist plot to bomb an airliner — significantly damaged our national security.
2. The United States and its allies were trying to locate a master bomb builder affiliated with Al Qaeda in the Arabian Peninsula, a group that was extremely difficult to penetrate. After considerable effort and danger, an agent was inserted inside the group. Although that agent succeeded in foiling one serious bombing plot against the United States, he was rendered ineffective once his existence was disclosed.
3. The leak of such sensitive source information not only denies us an invaluable insight into our adversaries’ plans and operations. It is also devastating to our overall ability to thwart terrorist threats, because it discourages our allies from working and sharing intelligence with us and deters would-be sources from providing intelligence about our adversaries. Unless we can demonstrate the willingness and ability to stop this kind of leak, those critical intelligence resources may be lost to us.
4. At the time the article was published, there were strong bipartisan calls for the Justice Department to find the leaker. Attorney General Eric H. Holder Jr. gave that assignment to Ronald C. Machen Jr., the United States attorney for the District of Columbia, who is known for his meticulous and dedicated work.
5. Importantly, his assignment was to identify and prosecute the government official who leaked the sensitive information; it was not to conduct an inquiry into the news organization that published it.

How the investigation was conducted

1. His office, which has an experienced national security team, undertook a methodical and measured investigation. Did prosecutors immediately seek the reporters’ toll records? No. Did they subpoena the reporters to testify or compel them to turn over their notes? No. Rather, according to the Justice Department’s May 14 letter to The A.P., they first interviewed 550 people, presumably those who knew or might have known about the agent, and scoured the documentary record. But after eight months of intensive effort, it appears that they still could not identify the leaker.
2. It was only then — after pursuing “all reasonable alternative investigative steps,” as required by the department’s regulations — that investigators proposed obtaining telephone toll records (logs of calls made and received) for about 20 phone lines that the leaker might have used in conversations with A.P. journalists. They limited the request to the two months when the leak most likely occurred, and did not propose more intrusive investigative steps.
3. The decision was made at the highest levels of the Justice Department, under longstanding regulations that are well within the boundaries of the Constitution. Having participated in similar decisions, we know that they are made after careful deliberation, because the government does not lightly seek information about a reporter’s work. Along with the obligation to investigate and prosecute government employees who violate their duty to protect operational secrets, Justice Department officials recognize the need to minimize any intrusion into the operations of the free press.

While we cannot know all of the facts and considerations that went into the department’s decision, we do know that prosecutors were right to try to find out who gave this damaging information to The A.P. They were right to pursue the investigation with “alternative investigative steps” for EIGHT MONTHS first. And ultimately, they were right to take it to the next stage when they still needed more to make a case against the leaker. If the Justice Department had not done so, it would have defaulted on its obligation to protect the American people.

http://www.nytimes.com/2013/05/21/opinion/stop-the-leaks.html