Here is background on the history of Article 3 from the ICRC (edited, original at link):
Up to 1949, the Geneva Conventions were designed to assist only the victims of wars between States. The principle of respect for human personality, the basis on which all the Conventions rest, had found expression in them only in its application to military personnel. Actually, however, it was concerned with people as human beings, without regard to their uniform, their allegiance, their race or their beliefs, without regard even to any obligations which the authority on which they depended might have assumed in their name or in their behalf. There is nothing astonishing, therefore, in the fact that the Red Cross has long been trying to aid the victims of civil wars and internal conflicts, the dangers of which are sometimes even greater than those of international wars. But in this connection particularly difficult problems arose. In a civil war, the lawful Government, or that which so styles itself, tends to regard its adversaries as common criminals. This attitude has sometimes led governmental authorities to look upon relief given by the Red Cross to victims on the other side as inadmissible aid to guilty parties. This conception still prevailed when the International Red Cross Conference in 1912 refused to consider a draft Convention on the role of the Red Cross in the event of civil war or insurrection. The Red Cross was not discouraged. In spite of frequent lack of understanding on the part of the authorities, it was able in some cases to carry out a certain amount of humanitarian work in civil conflicts. The question was again placed on the agenda of the Xth International Red Cross Conference in 1921, and a resolution was passed affirming the right of all victims of civil wars or social or revolutionary disturbances to relief in conformity with the general principles of the Red Cross. The resolution, as such, had not the force of a Convention, but it enabled the International Committee in at least two cases -- the civil war at the time of the 1921 plebiscite in Upper Silesia and the civil war in Spain -- to induce both sides to give some kind of undertaking to respect the principles of the Geneva Convention. Observing these results, the XVIth International Red Cross Conference, held at London in 1938, passed the following resolution which did much to supplement and strengthen that of 1921:
ARTICLE 3 (1):
In the case of armed conflict not of an international character occurring in the territory of one of the High Contracting Parties, each Party to the conflict shall be bound to apply, as a minimum, the following provisions:
(1) Persons taking no active part in the hostilities, including members of armed forces who have laid down their arms and those placed ' hors de combat ' by sickness, wounds, detention, or any other cause, shall in all circumstances be treated humanely, without any adverse distinction founded on race, colour, religion or faith, sex, birth or wealth, or any other similar criteria. To this end, the following acts are and shall remain prohibited at any time and in any place whatsoever with respect to the above-mentioned persons:
(a) violence to life and person, in particular murder of all kinds, mutilation, cruel treatment and torture;
(b) taking of hostages;
(c) outrages upon personal dignity, in particular humiliating and degrading treatment;
(d) the passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court, affording all the judicial guarantees which are recognized as indispensable by civilized peoples.
http://www.icrc.org/ihl.nsf/0/e160550475c4b133c12563cd0051aa66?OpenDocumentIn its Hamdan decision, the Supreme Court held that Common Article 3 of the Geneva Convention, which traditionally applies to domestic rebellion, should also apply to members of al Qaeda.
Any Congressional rewriting could also apply to American citizens who are accused of "domestic rebellion". The Article is clear on "armed conflict not of an international character". It protects those "persons taking no active part in the hostilities". There are possible scenarios arising from this that are truly frightening. The torture of people like the Chicago Seven and Terry Nichols come to mind.
Can you imagine how Dick Cheney would interpret this?
PS: I am not a legal scholar. Any expansions or corrections appreciated.