President Obama's plan to close the military detention facility at Guantanamo Naval Station in Cuba contained a noticeable amount of latitude. It may well be the case that practical ambiguities sometimes trump theoretical certainties.
The existence of the facility in Cuba is not necessarily the result of malign motives, war criminals or pell-mell abandonment of fundamental principles. It might just be the case that establishing the facility was an attempt to deal with a vexing and grave problem within constraints imposed by general principles. A tough legal and moral challenge arises when conventional military forces encounter enemies that do not observe accepted standards of conduct, and whose rogue activities intentionally put at risk non-combatants and other innocents.
This is not the first time in history such issues have arisen. The common law concept of "outlawry," in which criminals were deprived of any protection of the law as a result of their non-observance of it, is an analogous situation. Note that the outlaw, once declared, could be killed with impunity, as he could not seek protection of the law. Prior to the Nuremburg Trials, the English Chancellor, Lord Simon suggested that Allied forces resurrect the principle of outlawry so that Nazi war criminlas could be summarily executed. Churchill was sympathetic to this suggestion, but the United Staes and Soviets insisted on the more formal requirements of a trial.
No doubt, there were those dissenters from the concept of outlawry who argued that declaring the law not applicable to certain persons was a rejection of the concept of laws, and doing so was sacrificing the very thing that was sought to be protected. And doubtless, these concerns were dismissed with the observation that the surest way of sacrificing the thing to be defended was by refusing to defend it, not only with words and rhetoric, but by violence if necessary.
The claim that Americans are sacrificing their principles by balancing them against existential threats is simply an invalid generalization that may be nurtured in the academy but orphaned in the real world. It is comforting to think that in a civilized society, no one would forfeit his life to the state without a trial. This airy notion is refuted by the fact that even in civilized societies, police carry guns, and sometimes use them to deadly effect without a priori concurrence of judge and jury. It takes little deductive reasoning to conclude that sometimes justified homicide occurs without due process of law.
Ideals by their very nature are concerned with perfection; otherwise they are not ideals. But human affairs by their nature are seldom perfect. If they were, there would be no need for Guantanamo, no need for rules of war and no need for policemen. Recognizing that real world threats often do not accommodate idealistic responses is not abandoning principles; it is recognizing that such principles do not spring immaculately from the breasts of chattering and self-important critics, but that they must be fought for continually by good and honorable people, sometimes in ways that are ugly.
None of this is to say that Guantanamo should or should not close, that the detainees there should or should not have recourse to habeas corpus, or that they should or should not be given the protections of the Geneva Conventions (incidentally, the explicit exclusion of non-uniformed combatants from GC protocols was felt necessary to protect non-combatants). It is merely to point out that those who wish to fight terrorists with platitudes should not expect to be taken seriously when real people are slaughtered because the choices are hard and the theories just didn't work out very well.