In a regular war, a P.O. W. is usually a soldier dressed in the uniform of his state who has been shooting at you and has been captured.  The Geneva Code convention allows you to stick him in a camp, ask him his serial number and hold him until there is an exchange or the end of the war.

In the so-called war on terror, the 'terrorists' do not come with identifying brands.  Even if you sweep people up from a battlefield you do not know whether you have captured enemies intending to attack you, civilians got up in the crossfire, individuals who were duped or forced into fighting you (from where I am coming from any child soldier is a victim not a terrorist) or patriots who believe they are defending their country on their soil from your attack.

So when you have such a grab bag of individuals and stick them in Gitmo and torture some of them, there are only a few whom you can convict on the basis of court-admissible evidence.  So what do you do with the rest?

There is no government with whom you could (or would want to) organize an exchange.  There is no foreseeable endpoint until the last angry man dies without perpetuating his cause.  (See 400 years of Irish history.)

If you are following a criminal offense model you let the rest go.  If you are looking at whether some of these individuals intend to harm the United States you let none of them go because you cannot tell. 

If you believe, on the basis of 'evidence' obtained through torture, that one such individual intends to harm the United States you do not want to put him on trial because such evidence is not admissible and the court may set him free and the public exposure of the torture would further harm the U.S. image in the short term and endanger current soldiers because of the justified rage such torture evokes. It is simply fact that the exposure of the wrongs done at Abu Grahb made recruiting easier for Al Qaeda in the same way that the pictures of the burned bodies of four Americans made us angry.  In the long term stopping torture and exposing the torturers and dealing with them through the American system of justice -- including impeachment -- would provide the best example to the world of how to deal with such a problem and in the long run decrease the rage against the United States.  If you incarcerate him because you either lack evidence or for fear revealing immoral methods by which you obtained evidence, you compound the wrong done that individual -- because you have conducted yourself improperly you deny him the opportunity to show you that you are mistaken and he was neither a terrorist nor a threat now.

Bush's solution was the presumption of guilt on the basis of one man's say so -- I, the President, say that this person is an enemy combatant and therefore we can incacerate him for as long as we like.

Obama has not yet solved this problem but he has made some important promises : this determination will not be made by one person alone nor by one branch of government alone.  The provisions by which this situation will be handled will be devised with input from all three branches  -- not some executive branch fiat.  The provisions devised with be in accordance with the rule of law -- by which I presume he means that the rules will make some sense, that the individuals will have some rights, that actions will not be arbitrary and that the applications of the rules will be fair.

Preventive detention of soldiers has long been the rule of war fare while preventive detention of individuals has long be abhorred in Anglo-Saxon jurisprudence.  The preventive detention of individuals suspected of participation in terrorism is somewhere in the middle on this continuum.  Deteriming a fair and secure way to handle such individuals will be very difficult to do justly.   I wish Obama luck --  as oldtimers here know I am not a fan of Obama's but here I think that he faced with a very difficult moral and strategic issue and has announced an approach to finding a solution through our system of government that makes sense.