A shackled detainee is transported by guards, including a female soldier, at Camp Delta detention center, Guantanamo Bay U.S. Naval Base, Cuba, in this photo from December 2006. Brennan Linsley/AP hide caption

itoggle caption Brennan Linsley/AP

Relatives of victims of the Sept. 11 attacks are periodically flown down to Guantanamo Bay, Cuba, to witness court proceedings against five men accused of plotting the attacks. For the witnesses of the most recent court session, the experience raised questions about justice, humanity and the ethics of the death penalty. Joe Raedle/Getty Images hide caption

itoggle caption Joe Raedle/Getty Images

Secretary of Defense Chuck Hagel. Ariel Zambelich/NPR hide caption

itoggle caption Ariel Zambelich/NPR

In this June 27, 2006, file photo U.S. military guards walk within Camp Delta at the Guantanamo Bay U.S. Naval Base, Cuba. The U.S. announced the transfer of four detainees from Guantanamo to Oman; one will go to Estonia. Brennan Linsley/AP hide caption

itoggle caption Brennan Linsley/AP

Cooperative captives conduct afternoon prayers inside a communal cellblock at Camp 6 last month at the U.S. Navy base at Guantanamo Bay, Cuba. Six long-time detainees of the prison have been transferred to Uruguay. Walter Michot/MCT/Landov hide caption

itoggle caption Walter Michot/MCT/Landov

Jason Wright, seen here during his 15-month deployment to Iraq, served in the military for nine years before resigning last week. Courtesy of Jason Wright hide caption

itoggle caption Courtesy of Jason Wright

Moazzam Begg in front of the U.S. Embassy in London in 2006. Alastair Grant /AP hide caption

itoggle caption Alastair Grant /AP

A view of the the U.S. Naval Station base in Guantanamo Bay, Cuba. Guards and prisoners fought Saturday as inmates were moved into individual cells instead of communal housing. Suzette Laboy/AP hide caption

itoggle caption Suzette Laboy/AP

Books in the detainees library at the U.S. Naval Base in Guantanamo Bay, Cuba, are seen in this Aug. 8, 2013, photo. A prisoner at the facility handed over a copy of Fifty Shades of Grey to his lawyer. AFP/AFP/Getty Images hide caption

itoggle caption AFP/AFP/Getty Images

To raise awareness about force-feeding, Yasiin Bey, the musician and actor formerly known as Mos Def, in a video voluntarily underwent the same procedure administered to prisoners who refuse solid food in political protest while they are held in Guantanamo Bay. Reprieve/Asif Kapadia hide caption

itoggle caption Reprieve/Asif Kapadia

President Obama speaks about his administration's drone and counterterrorism policies at the National Defense University on Thursday. Saul Loeb/AFP/Getty Images hide caption

itoggle caption Saul Loeb/AFP/Getty Images