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In the last comprehensive review of prisoners held at Guantanamo Bay, the U.S. government decided nearly 50 were "too dangerous to transfer but not feasible for prosecution," leaving them in an open-ended legal limbo.

Now it seems many may not be so dangerous after all.

A review board that includes military and intelligence officials has been taking a hard look at these men and helping to steadily chip away at the list of indefinite detainees, who are a significant obstacle to President Barack Obama's push to shut down the detention center at the U.S. military base in Cuba.

The first 23 decisions announced by the Periodic Review Board as of this month have skewed heavily in favor of the prisoners. It has unanimously cleared 19 for release, and said five will continue to be held but will be re-evaluated again later. Some of the approved have already left Guantanamo while the rest are expected to depart over the summer.

Lawyers for detainees welcomed the initial results, although they say the men shouldn't have been held without charge for so long in the first place.

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"These people have not been reviewed in over six years. They have changed, circumstances have changed, and they have needed a fresh look," said Pardiss Kebriaei, a lawyer for the New York-based Center for Constitutional Rights who represented a prisoner cleared by the Periodic Review Board.

The deliberations of the board are private. But David Glazier, a professor at Loyola Law School who has analyzed records of the proceedings released by the Pentagon, said the members appear to be treating past assessments of prisoners "with a healthier degree of skepticism" than officials did in the past.

"If you just care about justice for human beings it's a little odd that it's taken 14 years to ask the questions in a hard enough way to discover that," said Glazier, a former Navy officer and expert in military law.

Detainees approved for release by the board over the past two years have included a Saudi accused of being a bodyguard for Osama bin Laden who waged one of the longest hunger strikes while at Guantanamo and a Kuwaiti who was alleged to be a "spiritual adviser" to the al-Qaida leader, though he would only have been about 20 at the time.

A Yemeni prisoner was cleared in January after authorities determined he was just a low-level jihadist fighter but had been mistaken for an al-Qaida facilitator or courier with a similar alias.

In Congress, where there is strong opposition to closing the detention center, the administration is seen as moving too fast to release men some fear will resume the behavior that got them locked up in the first place. "The administration's mad rush to push detainees on allies and partners has to stop," Rep. Ed Royce, a California Republican who is chairman of the Foreign Affairs Committee, said in January after 10 prisoners on the cleared list of 2010 were sent to Oman for resettlement.

There are 91 men held at Guantanamo, down from nearly 250 when Obama assumed the presidency. Those left include 36 who are cleared for release if security conditions can be met in the countries where they will settle. Seven face trial by military commission, including five charged with planning and supporting the terrorist attack of Sept. 11, 2001. Three others have been convicted.

The Obama administration wants to close the detention center and hopes to overcome the opposition in Congress to moving any prisoners to the U.S. by bringing down the population at Guantanamo to what officials have called the "irreducible minimum."

The administration says it has no plans to go further and turn the base itself over to Cuba — a demand Obama is likely to hear during his visit to Havana starting Sunday.

The January 2010 review designated 48 men for indefinite detention under the international law of war until the end of hostilities, a vague time frame in the war against terrorist groups such as al-Qaida. It also said 44 other detainees should be considered for prosecution. But few can now be tried due to court rulings that limited the jurisdiction of military commissions and the ban on sending them to the U.S., where they might otherwise be tried in federal court.

Men from both categories are now eligible to go before the Periodic Review Board, including some not likely to be released.

"There are people in the Guantanamo Bay detention facility who it is not safe to transfer ... They have to stay in U.S. detention," Defense Secretary Ash Carter told reporters last month.

The board is made up of representatives of six agencies, including the Defense Department, Justice Department and Office of the Director of National Intelligence. They convene in Arlington, Virginia, while the detainee sits in a trailer on the base, one foot shackled to the floor. They communicate by video teleconference.

Board members consider not just past allegations, but whether the detainee could pose a threat in the future, weighing such factors as his behavior while in custody and what he might do after Guantanamo, said David Remes, a Washington-based lawyer who has represented four detaineees cleared by the board.

"These guys have been held at Guantanamo for 14 plus years, most of them. It's not that surprising that after all this time the board concludes that they are no longer significant threats," Remes said.

The Director of National Intelligence reported this month that 5 percent of Guantanamo prisoners released since January 2009, when the U.S. began using the multi-agency screening process, have re-engaged in terrorism and 8 percent are suspected of it. That compares to 21 percent confirmed and 14 percent suspected under the earlier system.

Typical of those cleared for release by the PRB is Ghaleb al-Bihani. Born in Saudi Arabia but a citizen of Yemen, he traveled to Afghanistan as a 22-year-old and trained at an al-Qaida camp. His lawyers told the board he worked as an assistant cook. When he appeared before the board, he assured the members he would lead a peaceful life, that all he wanted was to get out of Guantanamo, get an education and find a wife. He has studied English and Spanish while at Guantanamo and asked the board to send him to Europe, Latin America, Asia or Qatar.

"I am against violence and I want to build a new life," he said, according to a transcript released by the Pentagon.

He may get that chance. The Pentagon announced about a month after his hearing that he was cleared for release. But that was two years ago and his lawyer says his departure is long overdue.

"Most of these men want to forget about this chapter, want to forget that Guantanamo ever happened to them," Kebriaei said.