As of May 18, 2010, Ali Yahya Mahdi al Raimi has been held at Guantanamo for eight years.
Combatant Status Review Tribunal
Initially the Bush administration asserted that they could withhold all the protections of the Geneva Conventions to captives from the war on terror. This policy was challenged before the Judicial branch. Critics argued that the USA could not evade its obligation to conduct a competent tribunals to determine whether captives are, or are not, entitled to the protections of prisoner of war status.
Subsequently the Department of Defense instituted the Combatant Status Review Tribunals. The Tribunals, however, were not authorized to determine whether the captives were lawful combatants -- rather they were merely empowered to make a recommendation as to whether the captive had previously been correctly determined to match the Bush administration's definition of an enemy combatant.