Jill Lepore, a staff writer, has been contributing to The New Yorker since 2005.

On November 13, 2001, George W. Bush, acting as President and Commander-in-Chief, signed a military order concerning the “Detention, Treatment, and Trial of Certain Non-Citizens in the War Against Terrorism.” Under its provisions, suspected terrorists who are not citizens of the United States were to be “detained at an appropriate location designated by the Secretary of Defense.” If brought to trial, they were to be tried and sentenced by a military commission. No member of the commission need be a lawyer. The ordinary rules of military law would not apply. Nor would the laws of war. Nor, in any conventional sense, would the laws of the United States. In the language of the order, “It is not practicable to apply in military commissions under this order the principles of law and the rules of evidence generally recognized in the trial of criminal cases in the United States district courts.”

“You’ve got to be kidding me,” Attorney General John Ashcroft reportedly said when he read an early draft, in which members of the commissions, as well as attorneys for both the prosecution and the defense, were to be selected by the Secretary of Defense. As Jess Bravin, the Wall Street Journal’s Supreme Court correspondent, reports in “The Terror Courts: Rough Justice at Guantánamo Bay,” Ashcroft expected the prosecution of people involved in 9/11 to be handled criminally, by his department, as had been done, successfully, with earlier terrorism cases. Other senior advisers had not been consulted. Condoleezza Rice and Colin Powell learned that Bush had signed the order only when they saw the news reported on television. In the final draft, the Department of Justice was left out altogether. Suspected terrorists could be imprisoned without charge, denied knowledge of the evidence against them, and, if tried, sentenced by courts following no previously established rules....