Applying different standards to al Qaeda does not abandon Geneva, but only recognizes that the U.S. faces a stateless enemy never contemplated by the Conventions.
Congress has created and funded a huge peacetime military that has substantial abilities to wage offensive operations, and it has not placed restrictions on the use of that military or the funds to support it, because it would rather let the president take the political risks in deciding on war. If Congress wanted to play a role in restricting war, it could - it simply does not want to. But we should not mistake a failure of political will for a violation of the Constitution.
There are pros and cons about the policy decision whether to follow the Geneva Conventions in a war where they do not legally apply. Among the pros might be benefits for America's image, its ability to argue in future conflicts that the Conventions should be followed, and training soldiers to follow only the Geneva standards. Among the cons might be greater security and safety for our troops who capture and detain al Qaeda operatives and the ability to gather more actionable intelligence swiftly.
It is important to recognize the differences between the war in Iraq and the war on terrorism. The treatment of those detained at Abu Ghraib is governed by the Geneva Conventions, which have been signed by both the U.S. and Iraq.
We can guess that the unacceptable conduct of the soldiers at Abu Ghraib resulted in part from the dangerous state of affairs on the ground in a theater of war.
In light of the Abu Ghraib prison scandal, critics are arguing that abuses of Iraqi prisoners are being produced by a climate of disregard for the laws of war.