There is nothing to understand. The USA under President Obama subscribes to The Geneva Conventions.

Spencer Akerman and Dan Roberts

The Guardian
Tuesday 25 February 2014

(President) Barack Obama (click here) formally ordered the Pentagon on Tuesday to make plans for a full pullout of American troops from Afghanistan by the end of the year, pointing to a way out of the conflict that is reminiscent of his end to the Iraq campaign....

War is not murder. War is a conflict. It is governed by international laws. If the Republicans wanted to have trials of prisoners, they should have conducted it a long time ago.

President Obama does not answer to Hamid Karzai and it is his obligation to honor the international laws the USA subscribes to which maintains military power within the realm of civilized.

I know what war is and what war isn't. It is unfortunate the USA House doesn't. 

List of Signing Statements by George W. Bush (click here), "The Decider."

The end of war does not mean it continues through detentions of POWs and/or trials to maintain prisoners in detention. The detainees that remain in Gitmo will no longer be legitimately held by this year's end.

SECTION 11 (click here)
RELEAS E AND REPATRIATION OF PRISONERS OF W AR
AT THE CLOSE OF HOSTILITIES

Article 118

Prisoners of war shall be released and repatriated without delay after the cessation of active hostilities.
In the absence of stipulations to the above effect in any agreement concluded between the Parties to the conflict with a view to the cessation of hostilities, or failing any such agreement, each of the Detaining Powers shall itself establish and execute without delay a plan of repatriation in conformity with the principle laid down in the foregoing paragraph.
In either case, the measures adopted shall be brought to the knowledge of the prisoners of war.
The costs of repatriation of prisoners of war shall in all cases be equitably apportioned between the Detaining Power and the Power on which the prisoners depend. This apportionment shall be carried out on the following basis:
(a) If the two Powers are contigu ou s , the Power on wh ich the prisoners of war depend shall bear the costs of repatriation from the frontiers of the Detaining Power.
(b) If the two Powers are not contiguous, the Detaining Power shall bear the costs of transport of prisoners of war over its own territory as far as its frontier or its port of embarkation nearest to the territory of the Power on which the prisoners of war depend. The Parties concerned shall agree between themselves as to the equitable apportionment of the remaining costs of the repatriation. The conclusion of this agreement shall in no circumstances justify any delay in the repatriation of the prisoners of war.

Article 119

Repatriation shall be effected in conditions similar to those laid down in Articles 46 to 48 inclusive of the present Convention for the transfer of prisoners of war, having regard to the provisions of Article 118 and to those of the following paragraphs.
On repatriation, any articles of value impounded from prisoners of war under Article 18, and any foreign currency which has not been converted into the currency of the Detaining Power, shall be restored to them. Articles of value and foreign currency which, for any reason whatever, are not restored to prisoners of war on repatriation, shall be despatched to the Information Bureau set up under Article 122.
Prisoners of war shall be allowed to take with them their personal effects, and any correspondence and parcels which have arrived for them. The weight of such baggage may be limited, if the conditions of repatriation so require, to what each prisoner can reasonably carry. Each prisoner shall in all cases be authorized to carry at least twenty-five kilograms.
The other personal effects of the repatriated prisoner shall be left in the charge of the Detaining Power which shall have them forwarded to him as soon as it has concluded an agreement to this effect, regulating the conditions of transport and the payment of the costs involved, with the Power on which the prisoner depends.
Prisoners of war against whom criminal proceedings for an indictable offence are pending may be detained until the end of such proceedings, and, if necessary, until the completion of the punishment. The same shall apply to, prisoners of war already convicted for an indictable offence.
Parties to the conflict shall communicate to each other the names of any prisoners of war who are detained until the end of the proceedings or until punishment has been completed.
By agreement between the Parties to the conflict, commissions shall be established for the purpose of searching for dispersed prisoners of war and
of assuring their repatriation with the least possible delay.