WASHINGTON (AP) — A Brooklyn man in prison for terrorism may have a new opportunity to challenge his conviction because the government only recently told him how it obtained evidence it intended to use against him. It was through one of the National Security Agency's secret surveillance programs.

On Monday, the government notified Albanian citizen Agron Hasbajrami it had intended to use information from the warrantless surveillance program — something that federal law required him to be told in September 2011. Hasbajrami pleaded guilty in 2012 to a terrorism charge after admitting he tried to go to Pakistan to join a radical jihadist insurgent group. He was sentenced to 15 years in prison.

This week's notice is the third of its kind since the Justice Department last year pledged to review certain terrorism cases in order to provide a clearer picture of how classified evidence against defendants was gathered. Hasbajrami's is the first closed case in which such a notification was provided.

The new policy is one of the ripple effects from disclosures last year by former NSA systems analyst Edward Snowden. The Snowden leaks have prompted major reviews of the programs that collected and examined billions of electronic and telephone communications. President Barack Obama is considering reforms.

It's unclear what impact these after-the-fact notifications will have on criminal cases in U.S. courts — and how many cases could be affected.

In its letter to Hasbajrami, the government said the notification that it used additional warrantless surveillance against him is not necessarily grounds for him to withdraw his guilty plea or challenge his conviction. But that could ultimately be up to a judge to decide.

"The new filings show that warrantless surveillance has played a role in more criminal cases than the government has ever before admitted, and that it has been improperly withholding that fact from defendants for years," said Patrick Toomey, an attorney in the American Civil Liberties Union National Security Project.

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Last year, Snowden leaked documents that revealed the extent of some of the surveillance, including one program begun in 2008 that allows the government to read or listen to communications of non-Americans located outside the U.S. for counterterrorism purposes. Defending the programs, the Obama administration has provided even more information about how and when this particular surveillance was used.

These details gave some people accused of terrorism a clearer picture of what evidence might have been used against them that they didn't know about. And this prompted questions about why certain defendants weren't told about this particular surveillance.

The surveillance at issue in the Justice Department review covers communications of non-Americans outside the U.S. Under that provision, known as Section 702, the NSA can also sweep up the domestic communications of any American in contact with the terror suspect, even if those contacts have nothing to do with terrorism. The resulting sweeps are likely to have included emails and other data from tens of thousands of Americans over the past decade, experts have said.

Civil liberties groups challenged the constitutionality of this program in 2008, after it was added to the Foreign Intelligence Surveillance Act. Their case ultimately went to the Supreme Court, which found that they had no standing to challenge the law, because they had no proof that their communications were monitored.

That decision came in February 2013, months before the Snowden disclosures. But, during the course of the Supreme Court arguments, the government stated that it is the government's policy to tell a defendant if evidence derived from this particular surveillance program would be used against him or her.

At that point, no defendant in a terrorism case was aware that the surveillance authorized under that particular law had been used in gathering evidence against him.

That changed as a result of the review, and in October of last year, the government notified Jamshid Muhtorov that it intended to use evidence from this particular type of surveillance in its case against him. It was the first time the government made such a notification. Muhtorov, an Uzbek refugee living in Colorado, was accused in 2012 of trying to travel overseas to fight for a terrorist group. As a result of the government's notification, Muhtorov became the first person who can prove that the government used this surveillance on him. He is now challenging the constitutionality of the program.

"It's going to create a difficulty for some courts," said Jonathan Turley, a law professor at George Washington Law School. "It's very hard to get the cat to walk backward, once you've passed the sentencing stage."

In November 2013, the government made a similar notification to Mohamed Osman Mohamud, a Somali American who was convicted of plotting to set off a bomb in downtown Portland in 2010. Mohamud has not yet been sentenced.

Some, and not just at the Justice Department, don't think there will be a substantial impact.

"My sense is that the notice is less significant than many believe, and that a future Supreme Court decision on the validity of Section 702 isn't particularly likely in the short term_and maybe even in the long term," George Washington University law professor Orin Kerr wrote in an October blog posting.

Hasbajrami's attorney, Steve Zissou, said it's too early to tell exactly what this latest notification means for his client.

"Insofar as undoing his conviction, he actually got a very sweet deal," Zissou said. Hasbajrami could have faced up to 60 years in prison if he hadn't negotiated a deal with the government. Now he's serving 15 years in New Jersey. In December, Hasbajrami asked a judge to set aside his prison sentence, saying the indictment against him was vague and overly broad. His motion cited what he called "the government's ever-evolving definition of what it means to provide material support."

"The reality is that it is very much an open question," Ramzi Kassem, a law professor and expert on prisoners' rights at the City University of New York, said of what the implications for Hasbajrami. "His lawyer would have offered a very different assessment of those odds had he known that he could have mounted an unprecedented legal challenge to the constitutionality of the evidence used against his client."

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Associated Press writers Eric Tucker, Mark Sherman and Stephen Braun contributed to this report.