News that the U.S. Justice Department under former President Donald Trump seized phone records of three reporters has ignited concerns about government interference in journalists' work.

Although such seizures are rare, journalists and First Amendment advocates have highlighted the negative impact they have on reporting, and are pushing the Justice Department to reveal more about its decision to obtain the records.

Justice Department Investigations into Leaks Test US Press Freedom Protections

The that Trump's Justice Department obtained phone records from three national security reporters, covering a period from April to July 2017.

Justice Department Investigations into Leaks Test US Press Freedom Protections

The records included phone numbers of calls made to and from the targeted phones and the duration of each call, according to the They did not include the content of the conversations.

Justice Department Investigations into Leaks Test US Press Freedom Protections

The first learned of the seizure in May, when it received letters from the Justice Department. The letters did not disclose the purpose of the seizure, according to the , but during the timeframe, the reporters co-wrote stories on Russia's interference in the 2016 election.

It is hard to gauge how often subpoena requests for media records are made and the factors involved when they are granted or dismissed, said Ken Paulson, director of the Free Speech Center at Middle Tennessee State University.

But when the cases do arise, they often include factors that trouble First Amendment experts.

The incident has renewed calls for the Justice Department to explain its guidelines for handling such requests, with media advocates pointing to weaknesses that could allow for surveillance of journalists and sources, which in turn could inhibit reporting.

"[Journalists] are among the people in our society who keep an eye on government power and abuses of power," said Lucy Dalglish, who noted a ramping up of leak prosecutions during her 12 years as executive director of the Reporters Committee for Freedom of the Press (RCFP). "You can't do that unless you have independently gathered, high-quality information."

, the attorney general must sign off on a subpoena for reporter records and any seizures of news records should be treated as "extraordinary measures, not standard investigatory practices."

The guidelines state that the affected member of the media must be notified beforehand unless "such notice would pose a clear and substantial threat to the integrity of the investigation, risk grave harm to national security, or present an imminent risk of death or serious bodily harm."

In the case of the , the journalists were not told of the subpoena for their records until after it had taken place.

"The fact that they didn't notify here is of significant concern for the First Amendment and press freedom generally," Gabe Rottman, director of RCFP's Technology and Press Freedom Project, told VOA.

The RCFP has called on the Justice Department leadership to explain why the records were seized and why it decided advance notification was not required in this case.

The Department of Justice did not respond to VOA's emails requesting comment.

The cited a spokesperson who said that the department followed "established procedures" and that the target of the investigation was not journalists "but rather those with access to the national defense information who provided it to the media and thus failed to protect it as lawfully required."

Danielle Brian, executive director of the independent government watchdog Project on Government Oversight (POGO), believes the current Justice Department guidelines are "inadequate." She said they are not codified into law and don't reflect the "bright-line that should exist between the Justice Department's surveillance capacities and journalists."

Brian said she would like Congress to pass a federal shield law that the Senate Judiciary Committee approved in 2009 that would protect journalists from government overreach. But there are obstacles to that becoming a reality.

"The principal problem is precisely what you're seeing the Justice Department argue now," Brian said. "They want to have the flexibility to decide when they will exercise their surveillance powers without accountability and scrutiny."

Paulson, of Middle Tennessee State University, acknowledged that systems should be in place to protect state secrets. But, he said, the system to protect that information could be abused.

"If someone were indeed leaking state secrets that endanger the United States of America, you would want to have a system where the government could investigate where these highly damaging leaks occur," Paulson told VOA. "The problem is ... there's always the danger that those in power will abuse it to ferret out perceived enemies and even the score."